Every problem in the chapter beside the book’s answer, a chapter at a time as you scroll.

Chapter 2: Linear Functions

184 problems · 51 figures

Try It #1 §2.1 source ↗

If f(x) is a linear function, and ( 2,3 ) and ( 0,4 ) are points on the line, find the slope. Is this function increasing or decreasing?

Answer

m= 4−3 0−2 = 1 −2 = − 1 2 ; decreasing because m<0.

Try It #2 §2.1 source ↗

The population of a small town increased from 1,442 to 1,868 between 2009 and 2012. Find the change of population per year if we assume the change was constant from 2009 to 2012.

Answer

m= 1,868−1,442 2,012−2,009 = 426 3 = 142 people per year

Try It #3 §2.1 source ↗

Write the point-slope form of an equation of a line with a slope of –2 that passes through the point ( –2,2 ). Then rewrite it in the slope-intercept form.

Answer

y−2=−2( x+2 ) ; y=−2x−2

Try It #4 §2.1 source ↗

Write the point-slope form of an equation of a line that passes through the points (–1,3) and (0,0). Then rewrite it in the slope-intercept form.

Answer

y−0=−3( x−0 ) ; y=−3x

Try It #5 §2.1 source ↗

If f(x) is a linear function, with f(2)=–11, and f(4)=−25, find an equation for the function in slope-intercept form.

Answer

y=−7x+3

Try It #6 §2.1 source ↗

A new plant food was introduced to a young tree to test its effect on the height of the tree. Table 2 shows the height of the tree, in feet, x months since the measurements began. Write a linear function, H(x), where x is the number of months since the start of the experiment.

x 0 2 4 8 12
H(x) 12.5 13.5 14.5 16.5 18.5
Table 2

Answer

H(x)= 0.5x+ 12.5

2.1-1 §2.1 source ↗

Terry is skiing down a steep hill. Terry's elevation, E(t), in feet after t seconds is given by E(t)= 3000− 70t. Write a complete sentence describing Terry’s starting elevation and how it is changing over time.

Answer

Terry starts at an elevation of 3000 feet and descends 70 feet per second.

2.1-3 §2.1 source ↗

Jessica is walking home from a friend’s house. After 2 minutes she is 1.4 miles from home. Twelve minutes after leaving, she is 0.9 miles from home. What is her rate in miles per hour?

Answer

3 miles per hour

2.1-5 §2.1 source ↗

A boat is 100 miles away from the marina, sailing directly toward it at 10 miles per hour. Write an equation for the distance of the boat from the marina after t hours.

Answer

d(t)= 100− 10t

2.1-7 §2.1 source ↗

For the following exercises, determine whether the equation of the curve can be written as a linear function.

y= 1 4 x+6

Answer

Yes.

2.1-9 §2.1 source ↗

For the following exercises, determine whether the equation of the curve can be written as a linear function.

y=3 x 2 −2

Answer

No.

2.1-11 §2.1 source ↗

For the following exercises, determine whether the equation of the curve can be written as a linear function.

3 x 2 +5y=15

Answer

No.

2.1-13 §2.1 source ↗

For the following exercises, determine whether the equation of the curve can be written as a linear function.

−2 x 2 +3 y 2 =6

Answer

No.

2.1-15 §2.1 source ↗

For the following exercises, determine whether each function is increasing or decreasing.

f(x)=4x+3

Answer

Increasing.

2.1-17 §2.1 source ↗

For the following exercises, determine whether each function is increasing or decreasing.

a(x)=5−2x

Answer

Decreasing.

2.1-19 §2.1 source ↗

For the following exercises, determine whether each function is increasing or decreasing.

h(x)=−2x+4

Answer

Decreasing.

2.1-21 §2.1 source ↗

For the following exercises, determine whether each function is increasing or decreasing.

j(x)=12x−3

Answer

Increasing.

2.1-23 §2.1 source ↗

For the following exercises, determine whether each function is increasing or decreasing.

n(x)=−13x−2

Answer

Decreasing.

2.1-25 §2.1 source ↗

For the following exercises, find the slope of the line that passes through the two given points.

(2,4) and (4, 10)

Answer

3

2.1-27 §2.1 source ↗

For the following exercises, find the slope of the line that passes through the two given points.

(−1,4) and (5,2)

Answer

–13

2.1-29 §2.1 source ↗

For the following exercises, find the slope of the line that passes through the two given points.

(6,11) and (−4,3)

Answer

45

2.1-31 §2.1 source ↗

For the following exercises, given each set of information, find a linear equation satisfying the conditions, if possible.

f(−1)=4 and f(5)=1

Answer

f(x)= − 12x+ 72

2.1-33 §2.1 source ↗

For the following exercises, given each set of information, find a linear equation satisfying the conditions, if possible.

Passes through (1,5) and (4,11)

Answer

y=2x+3

2.1-35 §2.1 source ↗

For the following exercises, given each set of information, find a linear equation satisfying the conditions, if possible.

Passes through (−2, 8) and (4, 6)

Answer

y=−13x+223

2.1-37 §2.1 source ↗

For the following exercises, given each set of information, find a linear equation satisfying the conditions, if possible.

x intercept at (−5, 0) and y intercept at (0, 4)

Answer

y=45x+4

2.1-39 §2.1 source ↗

For the following exercises, find the slope of the lines graphed.

A coordinate plane displays a straight line. The x-axis is labeled from -6 to 6, and the y-axis is labeled from -6 to 6. The line has a negative slope, descending from left to right. It intersects the y-axis at the point (0, 5) and the x-axis at the point (4, 0). The line passes through points such as (0, 5), (4, 0) and extends infinitely in both directions as indicated by arrows at its ends.

Answer

−54

2.1-41 §2.1 source ↗

For the following exercises, write an equation for the lines graphed.

A Cartesian coordinate system is shown with both the x-axis and y-axis ranging from -6 to 6. A straight blue line is plotted, extending across the graph from the bottom-left to the top-right. The line passes through several grid points, including (-2, 0) on the x-axis, (0, 1) on the y-axis, and (2, 2). The line has a positive slope, rising one unit for every two units moved to the right.

Answer

y= 2 3 x+1

2.1-43 §2.1 source ↗

For the following exercises, write an equation for the lines graphed.

A Cartesian coordinate system graph displays a downward-sloping blue line. The line intersects the y-axis at (0, 3) and the x-axis at roughly (1.5, 0), extending infinitely.

Answer

y=−2x+3

2.1-45 §2.1 source ↗

For the following exercises, write an equation for the lines graphed.

A Cartesian coordinate system is shown with an x-axis labeled from -6 to 6 and a y-axis labeled from -6 to 6. A solid blue horizontal line is drawn at y=3, extending across the entire visible x-axis with arrows on both ends, indicating it continues infinitely in both directions.

Answer

y=3

2.1-47 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

x 0 5 10 15
g(x) 5 –10 –25 –40

Answer

Linear, g(x)=−3x+5

2.1-49 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

x 0 5 10 15
f(x) –5 20 45 70

Answer

Linear, f(x)=5x−5

2.1-51 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

x 0 2 4 6
g(x) 6 –19 –44 –69

Answer

Linear, g(x)= − 252x+ 6

2.1-53 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

x 2 4 6 8
f(x) –4 16 36 56

Answer

Linear, f(x)=10x−24

2.1-55 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

If f is a linear function, f(0.1)= 11.5,  andf(0.4)= –5.9, find an equation for the function.

Answer

f(x)= − 58x+ 17.3

2.1-57 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

Graph the function f on a domain of [–10,10]:fx)= 2, 500x+ 4, 000

Answer

A graph shows a straight line labeled 'f' on a coordinate plane. The x-axis ranges from -8 to 8 in increments of 1, and the y-axis ranges from -20000 to 25000 in increments of 5000. The line 'f' passes through the origin (0,0) and has a positive slope. Notable points on the line include (-4, -10000) and (4, 10000).

2.1-59 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

Table 4 shows the input, p, and output, q, for a linear function q. a. Fill in the missing values of the table. b. Write the linear function k.

p 0.5 0.8 12 b
q 400 700 a 1,000,000
Table 4

Answer

a. a=11,900; b=1000.1 b. q(p)= 1000p− 100

2.1-61 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

Graph the linear function f on a domain of [ −0.1,0.1 ] for the function whose slope is 75 and y-intercept is −22.5. Label the points for the input values of −0.1 and 0.1.

Answer

A 2D graph displays an x-axis from -0.1 to 0.1 and a y-axis from 10 to -30. A blue line segment ascends from approximately (-0.09, -30) to (0.09, -15).

2.1-63 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

Find the value of x if a linear function goes through the following points and has the following slope: (x,2), (−4,6), m= 3

Answer

x=−163

2.1-65 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

Find the equation of the line that passes through the following points: (a,b) and ( a,b+1 )

Answer

x=a

2.1-67 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

Find the equation of the line that passes through the following points: (a,0) and (c,d)

Answer

y= dc−ax− adc−a

2.1-69 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

A gym membership with two personal training sessions costs $125, while gym membership with five personal training sessions costs $260. What is cost per session?

Answer

$45 per training session.

2.1-71 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

A phone company charges for service according to the formula: C(n)= 24+ 0.1n, where n is the number of minutes talked, and C(n) is the monthly charge, in dollars. Find and interpret the rate of change and initial value.

Answer

The rate of change is 0.1. For every additional minute talked, the monthly charge increases by $0.1 or 10 cents. The initial value is 24. When there are no minutes talked, initially the charge is $24.

2.1-73 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

A city’s population in the year 1960 was 287,500. In 1989 the population was 275,900. Compute the rate of growth of the population and make a statement about the population rate of change in people per year.

Answer

The slope is −400. This means for every year between 1960 and 1989, the population dropped by 400 per year in the city.

2.1-75 §2.1 source ↗

For the following exercises, which of the tables could represent a linear function? For each that could be linear, find a linear equation that models the data.

Suppose that average annual income (in dollars) for the years 1990 through 1999 is given by the linear function: I(x)= 1054x+ 23, 286, where x is the number of years after 1990. Which of the following interprets the slope in the context of the problem?

a. As of 1990, average annual income was $23,286.

b. In the ten-year period from 1990–1999, average annual income increased by a total of $1,054.

c. Each year in the decade of the 1990s, average annual income increased by $1,054.

d. Average annual income rose to a level of $23,286 by the end of 1999.

Answer

c.

Try It #1 §2.2 source ↗

Graph f(x)=−34x+6 by plotting points.

Answer

A two-dimensional graph displays a coordinate plane with an x-axis ranging from -8 to 10 and a y-axis ranging from -8 to 8. A straight blue line is drawn, sloping downwards from left to right. Three distinct points are marked on this line with their coordinates: (0, 6), (4, 3), and (8, 0). Arrows at both ends indicate that the line extends infinitely.

Try It #2 §2.2 source ↗

Find a point on the graph we drew in Example 2 that has a negative x-value.

Answer

Possible answers include (−3,7), (−6,9), or (−9,11).

Try It #3 §2.2 source ↗

Graph f(x)=4+2x, using transformations.

Answer

A graph displays three linear equations: y = 2x + 4 (orange), y = 2x (teal), and y = x (dark blue), plotted on a Cartesian coordinate system with axes from -10 to 10.

Try It #4 §2.2 source ↗

Find the x-intercept of f(x)=14x−4.

Answer

(16, 0)

Try It #5 §2.2 source ↗

Given the function h(x)=2x−4, write an equation for the line passing through (0,0) that is

ⓐ parallel to h(x)

ⓑ perpendicular to h(x)

Answer

ⓐ f(x)=2x

ⓑ g(x)=− 1 2 x

Try It #6 §2.2 source ↗

A line passes through the points, (−2,−15) and (2,−3). Find the equation of a perpendicular line that passes through the point, (6,4).

Answer

y=–13x+6

Try It #7 §2.2 source ↗

Look at the graph in Figure 22 and identify the following for the function j(t):

ⓐ y-intercept

ⓑ x-intercept(s)

ⓒ slope

ⓓ Is j(t) parallel or perpendicular to h(t) (or neither)?

ⓔ Is j(t) an increasing or decreasing function (or neither)?

ⓕ Write a transformation description for j(t) from the identity toolkit function f(x)=x.

Answer

ⓐ (0,5)

ⓑ (5, 0)

ⓒ Slope -1

ⓓ Neither parallel nor perpendicular

ⓔ Decreasing function

ⓕ Given the identity function, perform a vertical flip (over the t-axis) and shift up 5 units.

2.2-1 §2.2 source ↗

If the graphs of two linear functions are parallel, describe the relationship between the slopes and the y-intercepts.

Answer

The slopes are equal; y-intercepts are not equal.

2.2-3 §2.2 source ↗

If a horizontal line has the equation f(x)=a and a vertical line has the equation x=a, what is the point of intersection? Explain why what you found is the point of intersection.

Answer

The point of intersection is (a,a). This is because for the horizontal line, all of the y coordinates are a and for the vertical line, all of the x coordinates are a. The point of intersection will have these two characteristics.

2.2-5 §2.2 source ↗

Explain how to find a line perpendicular to a linear function that passes through a given point.

Answer

First, find the slope of the linear function. Then take the negative reciprocal of the slope; this is the slope of the perpendicular line. Substitute the slope of the perpendicular line and the coordinate of the given point into the equation y=mx+b and solve for b. Then write the equation of the line in the form y=mx+b by substituting in m and b.

2.2-7 §2.2 source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

3y+x=12 −y=8x+1

Answer

neither parallel or perpendicular

2.2-9 §2.2 source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

6x−9y=10 3x+2y=1

Answer

perpendicular

2.2-11 §2.2 source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

y= 3 4 x+1 −3x+4y=1

Answer

parallel

2.2-13 §2.2 source ↗

For the following exercises, find the x- and y-intercepts of each equation

g(x)=2x+4

Answer

(–2, 0); (0, 4)

2.2-15 §2.2 source ↗

For the following exercises, find the x- and y-intercepts of each equation

k( x )=−5x+1

Answer

(15, 0); (0, 1)

2.2-17 §2.2 source ↗

For the following exercises, find the x- and y-intercepts of each equation

7x+2y=56

Answer

(8, 0); (0, 28)

2.2-19 §2.2 source ↗

For the following exercises, use the descriptions of each pair of lines given below to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

• Line 1: Passes through (−8,−55) and (10,89)

• Line 2: Passes through (9,−44) and (4,−14)

Answer

Line 1:m= 8
Line 2:m= –6
Neither

2.2-21 §2.2 source ↗

For the following exercises, use the descriptions of each pair of lines given below to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

• Line 1: Passes through (1,7) and (5,5)

• Line 2: Passes through (−1,−3) and (1,1)

Answer

Line 1:m= – 1 2
Line 2:m= 2
Perpendicular

2.2-23 §2.2 source ↗

For the following exercises, use the descriptions of each pair of lines given below to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

• Line 1: Passes through (2,5) and (5,−1)

• Line 2: Passes through (−3,7) and (3,−5)

Answer

Line 1:m= –2
Line 2:m= –2
Parallel

2.2-25 §2.2 source ↗

For the following exercises, use the descriptions of each pair of lines given below to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

Write an equation for a line parallel to g(x)=3x−1 and passing through the point (4,9).

Answer

g(x)=3x−3

2.2-27 §2.2 source ↗

For the following exercises, use the descriptions of each pair of lines given below to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

Write an equation for a line perpendicular to p(t)=3t+4 and passing through the point (3,1).

Answer

p(t)=−13t+2

2.2-29 §2.2 source ↗

For the following exercises, use the descriptions of each pair of lines given below to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

Find the point at which the line f(x)=2x+5 intersects the line g(x)=−3x−5.

Answer

(−2,1)

2.2-31 §2.2 source ↗

For the following exercises, use the descriptions of each pair of lines given below to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

Use algebra to find the point at which the line f(x)= 74x+ 45760 intersects the line g(x)= 43x+ 315.

Answer

(−175,53)

2.2-33 §2.2 source ↗

For the following exercises, match the given linear equation with its graph in Figure 24.

A coordinate plane displays six distinct lines, labeled A, B, C, D, E, and F, intersecting at various points. Line C is horizontal, passing through the origin. Lines A and B have positive slopes, with A appearing steeper than B. Lines D, E, and F have negative slopes, with F appearing the steepest. Lines A, B, C, and F all pass through the origin. Figure 24

f(x)=−3x−1

Answer

F

2.2-35 §2.2 source ↗

For the following exercises, match the given linear equation with its graph in Figure 24.

A coordinate plane displays six distinct lines, labeled A, B, C, D, E, and F, intersecting at various points. Line C is horizontal, passing through the origin. Lines A and B have positive slopes, with A appearing steeper than B. Lines D, E, and F have negative slopes, with F appearing the steepest. Lines A, B, C, and F all pass through the origin. Figure 24

f(x)=2

Answer

C

2.2-37 §2.2 source ↗

For the following exercises, match the given linear equation with its graph in Figure 24.

A coordinate plane displays six distinct lines, labeled A, B, C, D, E, and F, intersecting at various points. Line C is horizontal, passing through the origin. Lines A and B have positive slopes, with A appearing steeper than B. Lines D, E, and F have negative slopes, with F appearing the steepest. Lines A, B, C, and F all pass through the origin. Figure 24

f(x)=3x+2

Answer

A

2.2-39 §2.2 source ↗

For the following exercises, sketch a line with the given features.

An x-intercept of (–2, 0) and y-intercept of (0, 4)

Answer

A graph shows a coordinate plane with the x-axis ranging from -8 to 3 and the y-axis ranging from -8 to 8. A straight blue line, labeled 'f', extends infinitely in both directions, passing through the points (-2, 0) and (0, 4). The point (-2, 0) is marked on the x-axis, and the point (0, 4) is marked on the y-axis. The line has a positive slope, indicating an increasing function.

2.2-41 §2.2 source ↗

For the following exercises, sketch a line with the given features.

A y-intercept of (0, 3) and slope 25

Answer

A coordinate plane displays a straight line, labeled 'f', with a positive slope. The line intersects the y-axis at (0, 3) and extends through the grid from x-values of -6 to 6 and y-values of -6 to 6.

2.2-43 §2.2 source ↗

For the following exercises, sketch a line with the given features.

Passing through the points (–3, –4) and (3, 0)

Answer

A coordinate plane shows a line labeled f. The x-axis is labeled from -7 to 7, and the y-axis is labeled from -7 to 7. The line passes through the points (0, -2), (3, 0), and (-3, -4). Arrows at both ends of the line indicate that it extends infinitely in both directions.

2.2-45 §2.2 source ↗

For the following exercises, sketch the graph of each equation.

g(x)=−3x+2

Answer

A graph of a coordinate plane shows a line labeled f. The x-axis ranges from -6 to 6 and the y-axis ranges from -6 to 6. The line passes through the points (0, 2) and (1, 0) and extends indefinitely in both directions. The line has a negative slope.

2.2-47 §2.2 source ↗

For the following exercises, sketch the graph of each equation.

k(x)=23x−3

Answer

A graph displaying a linear function f on a coordinate plane. The x-axis and y-axis both range from -6 to 6, marked with integer increments. The line passes through (0, -3) and (4, 0).

2.2-49 §2.2 source ↗

For the following exercises, sketch the graph of each equation.

p(t)=−2+3t

Answer

A graph shows a coordinate plane with a horizontal t-axis and a vertical y-axis. A line labeled p is drawn, passing through (0, -2) on the y-axis and (1, 1). The line has a positive slope.

2.2-51 §2.2 source ↗

For the following exercises, sketch the graph of each equation.

x=−2

Answer

A graph on a Cartesian coordinate system shows a vertical line. The line passes through x = -2 and is parallel to the y-axis. The x-axis ranges from -6 to 5, and the y-axis ranges from -6 to 6.

2.2-53 §2.2 source ↗

For the following exercises, sketch the graph of each equation.

q(x)=3

Answer

A graph of the rectangular coordinate system with a horizontal line shown at y = 3. The x-axis ranges from -8 to 8, and the y-axis ranges from -10 to 10.

2.2-55 §2.2 source ↗

For the following exercises, sketch the graph of each equation.

x3−y4=1

Answer

A graph shows a Cartesian coordinate system with an x-axis from -6 to 6 and a y-axis from -6 to 6. A blue line with a positive slope passes through the points (0, -4.5) and (3, 0).

2.2-57 §2.2 source ↗

For the following exercises, sketch the graph of each equation.

3x=15

Answer

A graph on a Cartesian coordinate plane shows a single dark blue vertical line. The x-axis is labeled from -3 to 8, and the y-axis is labeled from -8 to 8. The vertical line intersects the x-axis at x = 5 and extends infinitely in both the positive and negative y-directions, parallel to the y-axis.

2.2-59 §2.2 source ↗

For the following exercises, sketch the graph of each equation.

If g(x) is the transformation of f(x)=x after a vertical compression by 3 4 , a shift right by 2, and a shift down by 4

ⓐ Write an equation for g(x).

ⓑ What is the slope of this line?

ⓒ Find the y-intercept of this line.

Answer

ⓐ g(x)= 0.75x− 5.5

ⓑ 0.75

ⓒ (0,−5.5)

2.2-61 §2.2 source ↗

For the following exercises,, write the equation of the line shown in the graph.

A graph displays a Cartesian coordinate system with x and y axes ranging from -6 to 6. A horizontal blue line is drawn at y=3, extending across the entire visible graph.

Answer

y=3

2.2-63 §2.2 source ↗

For the following exercises,, write the equation of the line shown in the graph.

A Cartesian coordinate plane displays a vertical blue line. The x-axis ranges from -6 to 6, and the y-axis ranges from -6 to 6. The line passes through the x-axis at -3 and extends infinitely in both positive and negative y-directions, representing the equation x = -3.

Answer

x=−3

2.2-65 §2.2 source ↗

For the following exercises, find the point of intersection of each pair of lines if it exists. If it does not exist, indicate that there is no point of intersection.

y= 3 4 x+1 −3x+4y=12

Answer

no point of intersection

2.2-67 §2.2 source ↗

For the following exercises, find the point of intersection of each pair of lines if it exists. If it does not exist, indicate that there is no point of intersection.

2x=y−3y+4x=15

Answer

(2, 7)

2.2-69 §2.2 source ↗

For the following exercises, find the point of intersection of each pair of lines if it exists. If it does not exist, indicate that there is no point of intersection.

5x+3y=−65 x−y=−5

Answer

(–10, –5)

2.2-71 §2.2 source ↗

For the following exercises, find the point of intersection of each pair of lines if it exists. If it does not exist, indicate that there is no point of intersection.

Find the equation of the line perpendicular to the line g(x)= − 0.01x+2.01 through the point (1, 2).

Answer

y=100x−98

2.2-73 §2.2 source ↗

For the following exercises, use the functions f(x)= − 0.1x+200 and g(x)= 20x+ 0.1.

Where is f(x) greater than g(x)? Where is g(x) greater than f(x)?

Answer

x< 1999 201 x> 1999 201

2.2-75 §2.2 source ↗

For the following exercises, use the functions f(x)= − 0.1x+200 and g(x)= 20x+ 0.1.

A cell phone company offers two plans for minutes.

• Plan A: $20 per month and $1 for every one hundred texts.

• Plan B: $50 per month with free unlimited texts.

How many texts would you need to send per month for plan B to save you money?

Answer

Less than 3000 texts

Try It #1 §2.3 source ↗

A company sells doughnuts. They incur a fixed cost of $25,000 for rent, insurance, and other expenses. It costs $0.25 to produce each doughnut.

ⓐ Write a linear model to represent the cost C of the company as a function of x, the number of doughnuts produced.
ⓑ Find and interpret the y-intercept.

Answer

ⓐ C(x)= 0.25x+ 25, 000

ⓑ The y-intercept is ( 0,25,000 ). If the company does not produce a single doughnut, they still incur a cost of $25,000.

Try It #2 §2.3 source ↗

A city’s population has been growing linearly. In 2008, the population was 28,200. By 2012, the population was 36,800. Assume this trend continues.

ⓐ Predict the population in 2014.

ⓑ Identify the year in which the population will reach 54,000.

Answer

ⓐ 41,100

ⓑ 2020

Try It #3 §2.3 source ↗

There is a straight road leading from the town of Timpson to Ashburn 60 miles east and 12 miles north. Partway down the road, it junctions with a second road, perpendicular to the first, leading to the town of Garrison. If the town of Garrison is located 22 miles directly east of the town of Timpson, how far is the road junction from Timpson?

Answer

21.57 miles

2.3-1 §2.3 source ↗

Explain how to find the input variable in a word problem that uses a linear function.

Answer

Determine the independent variable. This is the variable upon which the output depends.

2.3-3 §2.3 source ↗

Explain how to interpret the initial value in a word problem that uses a linear function.

Answer

To determine the initial value, find the output when the input is equal to zero.

2.3-5 §2.3 source ↗

Find the area of a parallelogram bounded by the y-axis, the line x=3, the line f(x)=1+2x, and the line parallel to f(x) passing through ( 2, 7 ).

Answer

6 square units

2.3-7 §2.3 source ↗

Find the area of a triangle bounded by the y-axis, the line f(x)=9– 6 7 x, and the line perpendicular to f(x) that passes through the origin.

Answer

20.012 square units

2.3-9 §2.3 source ↗

For the following exercises, consider this scenario: A town’s population has been decreasing at a constant rate. In 2010 the population was 5,900. By 2012 the population had dropped to 4,700. Assume this trend continues.

Predict the population in 2016.

Answer

2,300

2.3-11 §2.3 source ↗

For the following exercises, consider this scenario: A town’s population has been increased at a constant rate. In 2010 the population was 46,020. By 2012 the population had increased to 52,070. Assume this trend continues.

Predict the population in 2016.

Answer

64,170

2.3-13 §2.3 source ↗

For the following exercises, consider this scenario: A town has an initial population of 75,000. It grows at a constant rate of 2,500 per year for 5 years.

Find the linear function that models the town’s population P as a function of the year, t, where t is the number of years since the model began.

Answer

P(t)= 75, 000+ 2,500t

2.3-15 §2.3 source ↗

For the following exercises, consider this scenario: A town has an initial population of 75,000. It grows at a constant rate of 2,500 per year for 5 years.

If the function P is graphed, find and interpret the x- and y-intercepts.

Answer

(–30, 0) Thirty years before the start of this model, the town had no citizens. (0, 75,000) Initially, the town had a population of 75,000.

2.3-17 §2.3 source ↗

For the following exercises, consider this scenario: A town has an initial population of 75,000. It grows at a constant rate of 2,500 per year for 5 years.

When will the output reached 100,000?

Answer

Ten years after the model began.

2.3-19 §2.3 source ↗

For the following exercises, consider this scenario: The weight of a newborn is 7.5 pounds. The baby gained one-half pound a month for its first year.

Find the linear function that models the baby’s weight W as a function of the age of the baby, in months, t.

Answer

W(t)= 0.5t+ 7.5

2.3-21 §2.3 source ↗

For the following exercises, consider this scenario: The weight of a newborn is 7.5 pounds. The baby gained one-half pound a month for its first year.

If the function W is graphed, find and interpret the x- and y-intercepts.

Answer

( −15,0 ) : The x-intercept is not a plausible set of data for this model because it means the baby weighed 0 pounds 15 months prior to birth. ( 0, 7.5 ) : The baby weighed 7.5 pounds at birth.

2.3-23 §2.3 source ↗

For the following exercises, consider this scenario: The weight of a newborn is 7.5 pounds. The baby gained one-half pound a month for its first year.

When did the baby weigh 10.4 pounds?

Answer

At age 5.8 months.

2.3-25 §2.3 source ↗

For the following exercises, consider this scenario: The number of people afflicted with the common cold in the winter months steadily decreased by 205 each year from 2005 until 2010. In 2005, 12,025 people were afflicted.

Find the linear function that models the number of people inflicted with the common cold C as a function of the year, t.

Answer

C(t)= 12, 025− 205t

2.3-27 §2.3 source ↗

For the following exercises, consider this scenario: The number of people afflicted with the common cold in the winter months steadily decreased by 205 each year from 2005 until 2010. In 2005, 12,025 people were afflicted.

If the function C is graphed, find and interpret the x- and y-intercepts.

Answer

(58.7, 0) : In roughly 59 years, the number of people inflicted with the common cold would be 0. (0,12,025) : Initially there were 12,025 people afflicted by the common cold.

2.3-29 §2.3 source ↗

For the following exercises, consider this scenario: The number of people afflicted with the common cold in the winter months steadily decreased by 205 each year from 2005 until 2010. In 2005, 12,025 people were afflicted.

When will the number of people afflicted with the common cold reach 0?

Answer

2064

2.3-31 §2.3 source ↗

For the following exercises, use the graph in Figure 7, which shows the profit, y, in thousands of dollars, of a company in a given year, t, where t represents the number of years since 1980.

Graph of a line from (15, 150) to (25, 130). Figure 7

Find the linear function y, where y depends on t, the number of years since 1980.

Answer

y=−2t+180

2.3-33 §2.3 source ↗

For the following exercises, use the graph in Figure 7, which shows the profit, y, in thousands of dollars, of a company in a given year, t, where t represents the number of years since 1980.

Graph of a line from (15, 150) to (25, 130). Figure 7

Find and interpret the x-intercept.

Answer

In 2070, the company’s profit will be zero.

2.3-35 §2.3 source ↗

For the following exercises, use the graph in Figure 8, which shows the profit, y, in thousands of dollars, of a company in a given year, t, where t represents the number of years since 1980.

Graph of a line from (15, 150) to (25, 450). Figure 8

Find the linear function y, where y depends on t, the number of years since 1980.

Answer

y=30t−300

2.3-37 §2.3 source ↗

For the following exercises, use the graph in Figure 8, which shows the profit, y, in thousands of dollars, of a company in a given year, t, where t represents the number of years since 1980.

Graph of a line from (15, 150) to (25, 450). Figure 8

Find and interpret the x-intercept.

Answer

(10, 0) In 1990, the profit earned zero profit.

2.3-39 §2.3 source ↗

For the following exercises, use the median home values in Mississippi and Hawaii (adjusted for inflation) shown in Table 2. Assume that the house values are changing linearly.

Year Mississippi Hawaii
1950 $25,200 $74,400
2000 $71,400 $272,700
Table 2

In which state have home values increased at a higher rate?

Answer

Hawaii

2.3-41 §2.3 source ↗

For the following exercises, use the median home values in Mississippi and Hawaii (adjusted for inflation) shown in Table 2. Assume that the house values are changing linearly.

Year Mississippi Hawaii
1950 $25,200 $74,400
2000 $71,400 $272,700
Table 2

If we assume the linear trend existed before 1950 and continues after 2000, the two states’ median house values will be (or were) equal in what year? (The answer might be absurd.)

Answer

During the year 1933

2.3-43 §2.3 source ↗

For the following exercises, use the median home values in Indiana and Alabama (adjusted for inflation) shown in Table 3. Assume that the house values are changing linearly.

Year Indiana Alabama
1950 $37,700 $27,100
2000 $94,300 $85,100
Table 3

If these trends were to continue, what would be the median home value in Indiana in 2010?

Answer

$105,620

2.3-45 §2.3 source ↗

For the following exercises, use the median home values in Indiana and Alabama (adjusted for inflation) shown in Table 3. Assume that the house values are changing linearly.

Year Indiana Alabama
1950 $37,700 $27,100
2000 $94,300 $85,100
Table 3

In 2004, a school population was 1,001. By 2008 the population had grown to 1,697. Assume the population is changing linearly.

ⓐ How much did the population grow between the year 2004 and 2008?

ⓑ How long did it take the population to grow from 1,001 students to 1,697 students?

ⓒ What is the average population growth per year?

ⓓ What was the population in the year 2000?

ⓔ Find an equation for the population, P, of the school t years after 2000.

ⓕ Using your equation, predict the population of the school in 2011.

Answer

ⓐ 696 people

ⓑ 4 years

ⓒ 174 people per year

ⓓ 305 people

ⓔ P(t)= 305+ 174t

ⓕ 2,219 people

2.3-47 §2.3 source ↗

For the following exercises, use the median home values in Indiana and Alabama (adjusted for inflation) shown in Table 3. Assume that the house values are changing linearly.

Year Indiana Alabama
1950 $37,700 $27,100
2000 $94,300 $85,100
Table 3

A phone company has a monthly cellular plan where a customer pays a flat monthly fee and then a certain amount of money per minute used for voice and video calling. If a customer uses 410 minutes, the monthly cost will be $71.50. If the customer uses 720 minutes, the monthly cost will be $118.

ⓐ Find a linear equation for the monthly cost of the cell plan as a function of x, the number of monthly minutes used.

ⓑ Interpret the slope and y-intercept of the equation.

ⓒ Use your equation to find the total monthly cost if 687 minutes are used.

Answer

ⓐ C(x)= 0.15x+ 10

ⓑ The flat monthly fee is $10 and there is an additional $0.15 fee for each additional minute used

ⓒ $113.05

2.3-49 §2.3 source ↗

For the following exercises, use the median home values in Indiana and Alabama (adjusted for inflation) shown in Table 3. Assume that the house values are changing linearly.

Year Indiana Alabama
1950 $37,700 $27,100
2000 $94,300 $85,100
Table 3

In 1990, the moose population in a park was measured to be 4,360. By 1999, the population was measured again to be 5,880. Assume the population continues to change linearly.

ⓐ Find a formula for the moose population, P since 1991.

ⓑ What does your model predict the moose population to be in 2003?

Answer

ⓐ P(t)= 190t+ 4,360

ⓑ 6,640 moose

2.3-51 §2.3 source ↗

For the following exercises, use the median home values in Indiana and Alabama (adjusted for inflation) shown in Table 3. Assume that the house values are changing linearly.

Year Indiana Alabama
1950 $37,700 $27,100
2000 $94,300 $85,100
Table 3

The Federal Helium Reserve held about 16 billion cubic feet of helium in 2010 and is being depleted by about 2.1 billion cubic feet each year.

ⓐ Give a linear equation for the remaining federal helium reserves, R, in terms of t, the number of years since 2010.

ⓑ In 2015, what will the helium reserves be?

ⓒ If the rate of depletion doesn’t change, in what year will the Federal Helium Reserve be depleted?

Answer

ⓐ R(t)= 16− 2.1t

ⓑ 5.5 billion cubic feet

ⓒ During the year 2017

2.3-53 §2.3 source ↗

For the following exercises, use the median home values in Indiana and Alabama (adjusted for inflation) shown in Table 3. Assume that the house values are changing linearly.

Year Indiana Alabama
1950 $37,700 $27,100
2000 $94,300 $85,100
Table 3

You are choosing between two different prepaid cell phone plans. The first plan charges a rate of 26 cents per minute. The second plan charges a monthly fee of $19.95 plus 11 cents per minute. How many minutes would you have to use in a month in order for the second plan to be preferable?

Answer

More than 133 minutes

2.3-55 §2.3 source ↗

For the following exercises, use the median home values in Indiana and Alabama (adjusted for inflation) shown in Table 3. Assume that the house values are changing linearly.

Year Indiana Alabama
1950 $37,700 $27,100
2000 $94,300 $85,100
Table 3

When hired at a new job selling jewelry, you are given two pay options:

• Option A: Base salary of $17,000 a year with a commission of 12% of your sales

• Option B: Base salary of $20,000 a year with a commission of 5% of your sales

How much jewelry would you need to sell for option A to produce a larger income?

Answer

More than $42,857.14 worth of jewelry

2.3-57 §2.3 source ↗

For the following exercises, use the median home values in Indiana and Alabama (adjusted for inflation) shown in Table 3. Assume that the house values are changing linearly.

Year Indiana Alabama
1950 $37,700 $27,100
2000 $94,300 $85,100
Table 3

When hired at a new job selling electronics, you are given two pay options:

• Option A: Base salary of $20,000 a year with a commission of 12% of your sales

• Option B: Base salary of $26,000 a year with a commission of 3% of your sales

How much electronics would you need to sell for option A to produce a larger income?

Answer

$66,666.67

Try It #1 §2.4 source ↗

According to the data from Table 1, what temperature can we predict it is if we counted 20 chirps in 15 seconds?

Answer

54°F

Try It #2 §2.4 source ↗

Use the model we created using technology in Example 6 to predict the gas consumption in 2011. Is this an interpolation or an extrapolation?

Answer

150.871 billion gallons; extrapolation

2.4-1 §2.4 source ↗

Describe what it means if there is a model breakdown when using a linear model.

Answer

When our model no longer applies, after some value in the domain, the model itself doesn’t hold.

2.4-3 §2.4 source ↗

What is extrapolation when using a linear model?

Answer

We predict a value outside the domain and range of the data.

2.4-5 §2.4 source ↗

Explain how to interpret the absolute value of a correlation coefficient.

Answer

The closer the number is to 1, the less scattered the data, the closer the number is to 0, the more scattered the data.

2.4-7 §2.4 source ↗

A regression was run to determine whether there is a relationship between the diameter of a tree ( x, in inches) and the tree’s age ( y, in years). The results of the regression are given below. Use this to predict the age of a tree with diameter 10 inches.

y=ax+b a=6.301 b=−1.044 r=0.970

Answer

61.966 years

2.4-9 §2.4 source ↗

For the following exercises, draw a scatter plot for the data provided. Does the data appear to be linearly related?

1 2 3 4 5 6
46 50 59 75 100 136

Answer

No.

2.4-11 §2.4 source ↗

For the following exercises, draw a scatter plot for the data provided. Does the data appear to be linearly related?

1 3 5 7 9 11
1 9 28 65 125 216

Answer

No.

2.4-13 §2.4 source ↗

For the following exercises, draw a scatter plot for the data provided. Does the data appear to be linearly related?

For the following data, draw a scatter plot. If we wanted to know when the temperature would reach 28 °F, would the answer involve interpolation or extrapolation? Eyeball the line and estimate the answer.

Temperature, °F 16 18 20 25 30
Time, seconds 46 50 54 55 62

Answer

Interpolation. About 60° F.

2.4-15 §2.4 source ↗

For the following exercises, match each scatterplot with one of the four specified correlations in Figure 9 and Figure 10.

Two scatter plots (a) and (b) display randomly distributed blue points on a light background, illustrating a lack of discernible patterns or relationships within the data. Figure 9 Two scatter plots. Plot (c) shows data with a negative correlation, while plot (d) illustrates data with a positive correlation. Figure 10

r=−0.89

Answer

C

2.4-17 §2.4 source ↗

For the following exercises, match each scatterplot with one of the four specified correlations in Figure 9 and Figure 10.

Two scatter plots (a) and (b) display randomly distributed blue points on a light background, illustrating a lack of discernible patterns or relationships within the data. Figure 9 Two scatter plots. Plot (c) shows data with a negative correlation, while plot (d) illustrates data with a positive correlation. Figure 10

r=−0.39

Answer

B

2.4-19 §2.4 source ↗

For the following exercises, draw a best-fit line for the plotted data.

A scatter plot with an x-axis labeled from 0 to 10 and a y-axis labeled from 0 to 10. Several blue circular data points are scattered across the lower part of the plot, primarily between y=0 and y=3.5.

Answer

A scatter plot displays data points with a positive linear regression line. The orange line shows an upward trend among the blue data points, suggesting a positive correlation between the variables on the x and y axes.A scatter plot displays data points with a positive linear regression line. The orange line shows an upward trend among the blue data points, suggesting a positive correlation between the variables on the x and y axes.

2.4-21 §2.4 source ↗

For the following exercises, draw a best-fit line for the plotted data.

This scatter plot displays a series of data points across an x-axis from 0 to 10 and a y-axis from 0 to 10. The points illustrate a curvilinear, U-shaped relationship, initially decreasing from approximately y=2.5 at x=0 to a minimum around x=2 (y=3.0), and then steadily increasing to y=6.0 at x=10.

Answer

A scatter plot with blue data points showing a positive linear relationship, and an orange line representing the linear regression fit.A scatter plot with blue data points showing a positive linear relationship, and an orange line representing the linear regression fit.

2.4-23 §2.4 source ↗

For the following exercises, draw a best-fit line for the plotted data.

The U.S. import of wine (in hectoliters) for several years is given in Table 5. Determine whether the trend appears linear. If so, and assuming the trend continues, in what year will imports exceed 12,000 hectoliters?

YearImports
19922665
19942688
19963565
19984129
20004584
20025655
20046549
20067950
20088487
20099462
Table 5

Answer

Yes, trend appears linear because r=0.985 and will exceed 12,000 near midyear, 2016, 24.6 years since 1992.

2.4-25 §2.4 source ↗

For the following exercises, use each set of data to calculate the regression line using a calculator or other technology tool, and determine the correlation coefficient to 3 decimal places of accuracy.

x 8 15 26 31 56
y 23 41 53 72 103

Answer

y= 1.640x+ 13.800, r=0.987

2.4-27 §2.4 source ↗

For the following exercises, use each set of data to calculate the regression line using a calculator or other technology tool, and determine the correlation coefficient to 3 decimal places of accuracy.

x y x y
321.91115.76
422.221213.68
522.741314.1
622.261414.02
720.781511.94
817.61612.76
916.521711.28
1018.54189.1

Answer

y= − 0.962x+ 26.86, r= − 0.965

2.4-29 §2.4 source ↗

For the following exercises, use each set of data to calculate the regression line using a calculator or other technology tool, and determine the correlation coefficient to 3 decimal places of accuracy.

x 21 25 30 31 40 50
y 17 11 2 -1 -18 -40

Answer

y= − 1.981x+ 60.197; r=−0.998

2.4-31 §2.4 source ↗

For the following exercises, use each set of data to calculate the regression line using a calculator or other technology tool, and determine the correlation coefficient to 3 decimal places of accuracy.

x 900 988 1000 1010 1200 1205
y 70 80 82 84 105 108

Answer

y= 0.121x− 38.841, r= 0.998

2.4-33 §2.4 source ↗

For the following exercises, use each set of data to calculate the regression line using a calculator or other technology tool, and determine the correlation coefficient to 3 decimal places of accuracy.

Graph f(x)=−2x−10. Pick a set of 5 ordered pairs using inputs x= −2,  1,  5,  6,  9 and use linear regression to verify the function.

Answer

(−2,−6), (1,−12), (5,−20), (6,−22), (9,−28); y=−2x−10

2.4-35 §2.4 source ↗

For the following exercises, consider this scenario: The profit of a company decreased steadily over a ten-year span. The following ordered pairs shows dollars and the number of units sold in hundreds and the profit in thousands of dollars over the ten-year span, (number of units sold, profit) for specific recorded years:

(46, 1,600), (48, 1,550), (50, 1,505), (52, 1,540), (54, 1,495).

Find to the nearest tenth and interpret the x-intercept.

Answer

(189.8,0) If 18,980 units are sold, the company will have a profit of zero dollars.

2.4-37 §2.4 source ↗

For the following exercises, consider this scenario: The population of a city increased steadily over a ten-year span. The following ordered pairs shows the population and the year over the ten-year span, (population, year) for specific recorded years:

(2500, 2000), (2650, 2001), (3000, 2003), (3500, 2006), (4200, 2010)

Use linear regression to determine a function y, where the year depends on the population. Round to three decimal places of accuracy.

Answer

y= 0.00587x+ 1985.41

2.4-39 §2.4 source ↗

For the following exercises, consider this scenario: The profit of a company increased steadily over a ten-year span. The following ordered pairs show the number of units sold in hundreds and the profit in thousands of dollars over the ten year span, (number of units sold, profit) for specific recorded years:

(46, 250), (48, 305), (50, 350), (52, 390), (54, 410).

Use linear regression to determine a function y, where the profit in thousands of dollars depends on the number of units sold in hundreds .

Answer

y= 20.25x− 671.5

2.4-41 §2.4 source ↗

For the following exercises, consider this scenario: The profit of a company decreased steadily over a ten-year span. The following ordered pairs show dollars and the number of units sold in hundreds and the profit in thousands of dollars over the ten-year span (number of units sold, profit) for specific recorded years:

(46, 250), (48, 225), (50, 205), (52, 180), (54, 165).

Use linear regression to determine a function y, where the profit in thousands of dollars depends on the number of units sold in hundreds .

Answer

y= − 10.75x+ 742.50

2.R-1 §2.R source ↗

Determine whether the algebraic equation is linear. 2x+3y=7

Answer

Yes

2.R-3 §2.R source ↗

Determine whether the function is increasing or decreasing.

f(x)=7x−2

Answer

Increasing.

2.R-5 §2.R source ↗

Given each set of information, find a linear equation that satisfies the given conditions, if possible.

Passes through (7,5) and (3,17)

Answer

y=−3x+26

2.R-7 §2.R source ↗

Find the slope of the line shown in the line graph.

A two-dimensional Cartesian coordinate system shows a straight blue line. Both the x-axis and y-axis are scaled from -6 to 6. The line passes through the x-intercept at (1, 0) and the y-intercept at (0, -3), having a positive slope of 3.

Answer

3

2.R-9 §2.R source ↗

Write an equation in slope-intercept form for the line shown.

A graph displays a blue straight line on a Cartesian coordinate plane with x and y axes, each labeled from -6 to 6. The line has a positive slope, passing through the y-axis at (0, -2) and the x-axis at (1, 0).

Answer

y=2x−2

2.R-11 §2.R source ↗

Does the following table represent a linear function? If so, find the linear equation that models the data.

x 6 8 12 26
g(x) –8 –12 –18 –46

Answer

Not linear.

2.R-13 §2.R source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

2x−6y=12 −x+3y=1

Answer

parallel

2.R-15 §2.R source ↗

For the following exercises, find the x- and y- intercepts of the given equation

7x+9y=−63

Answer

(–9,0); (0,–7)

2.R-17 §2.R source ↗

For the following exercises, use the descriptions of the pairs of lines to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

• Line 1: Passes through (5,11) and (10,1)

• Line 2: Passes through (−1,3) and (−5,11)

Answer

Line 1: m=−2; Line 2: m=−2; Parallel

2.R-19 §2.R source ↗

For the following exercises, use the descriptions of the pairs of lines to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

Write an equation for a line perpendicular to f(x)=5x−1 and passing through the point (5, 20).

Answer

y=−0.2x+21

2.R-21 §2.R source ↗

For the following exercises, use the descriptions of the pairs of lines to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

Sketch a graph of the linear function f(t)=2t−5.

Answer

A coordinate plane showing a blue line passing through the points (0, -5) and (2.5, 0). The x-axis ranges from -4 to 6, and the y-axis ranges from -6 to 6.

2.R-23 §2.R source ↗

For the following exercises, use the descriptions of the pairs of lines to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

A car rental company offers two plans for renting a car.

• Plan A: 25 dollars per day and 10 cents per mile

• Plan B: 50 dollars per day with free unlimited mileage

How many miles would you need to drive for plan B to save you money?

Answer

250.

2.R-25 §2.R source ↗

For the following exercises, use the descriptions of the pairs of lines to find the slopes of Line 1 and Line 2. Is each pair of lines parallel, perpendicular, or neither?

A town’s population increases at a constant rate. In 2010 the population was 55,000. By 2012 the population had increased to 76,000. If this trend continues, predict the population in 2016.

Answer

118,000.

2.R-27 §2.R source ↗

For the following exercises, use the graph in Figure 1 showing the profit, y, in thousands of dollars, of a company in a given year, x, where x represents years since 1980.

A line graph showing a linear decrease. The line starts at approximately (5, 10,000) and descends to approximately (25, 4,000), indicating a negative relationship between x and y. Figure 1

Find the linear function y, where y depends on x, the number of years since 1980.

Answer

y= − 300x+ 11, 500

2.R-29 §2.R source ↗

For the following exercise, consider this scenario: In 2004, a school population was 1,700. By 2012 the population had grown to 2,500.

Assume the population is changing linearly.

ⓐ How much did the population grow between the year 2004 and 2012?

ⓑ What is the average population growth per year?

ⓒ Find an equation for the population, P, of the school t years after 2004.

Answer

a) 800; b) 100 students per year; c) P(t)= 100t+ 1700

2.R-31 §2.R source ↗

For the following exercises, consider this scenario: In 2000, the moose population in a park was measured to be 6,500. By 2010, the population was measured to be 12,500. Assume the population continues to change linearly.

What does your model predict the moose population to be in 2020?

Answer

18,500

2.R-33 §2.R source ↗

For the following exercises, consider this scenario: The median home values in subdivisions Pima Central and East Valley (adjusted for inflation) are shown in Table 1. Assume that the house values are changing linearly.

Year Pima Central East Valley
1970 32,000 120,250
2010 85,000 150,000
Table 1

If these trends were to continue, what would be the median home value in Pima Central in 2015?

Answer

$91,625

2.R-35 §2.R source ↗

For the following exercises, consider this scenario: The median home values in subdivisions Pima Central and East Valley (adjusted for inflation) are shown in Table 1. Assume that the house values are changing linearly.

Year Pima Central East Valley
1970 32,000 120,250
2010 85,000 150,000
Table 1

Draw a scatter plot for the data in Table 3. If we wanted to know when the population would reach 15,000, would the answer involve interpolation or extrapolation?

YearPopulation
19905,600
19955,950
20006,300
20056,600
20106,900
Table 3

Answer

Extrapolation.

A scatter plot shows the population from 1990 to 2010. The population steadily increased, starting at 5,600 in 1990 and rising to 6,900 in 2010.

2.R-37 §2.R source ↗

For the following exercises, consider this scenario: The median home values in subdivisions Pima Central and East Valley (adjusted for inflation) are shown in Table 1. Assume that the house values are changing linearly.

Year Pima Central East Valley
1970 32,000 120,250
2010 85,000 150,000
Table 1

Draw a best-fit line for the plotted data.

A scatter plot shows five data points generally trending upwards. The x-axis ranges from 0 to 12, and the y-axis ranges from 0 to 120.

Answer

A two-dimensional scatter plot displays six data points with an upward-sloping orange line, indicating a positive linear trend. The x-axis is labeled 'x' and ranges from 0 to 12, with major tick marks every 2 units. The y-axis is labeled 'y' and ranges from 0 to 120, with major tick marks every 20 units. The plotted points are approximately (2, 75), (3, 88), (4, 82), (6, 84), (8, 89), and (10, 98). The orange line represents a linear regression fit to these data points.

2.R-39 §2.R source ↗

For the following exercises, consider the data in Table 5, which shows the percent of unemployed in a city of people 25 years or older who are college graduates is given below, by year.

Year 2000 2002 2005 2007 2010
Percent Graduates 6.5 7.0 7.4 8.2 9.0
Table 5

In what year will the percentage exceed 12%?

Answer

Midway through 2024.

2.R-41 §2.R source ↗

For the following exercises, consider the data in Table 5, which shows the percent of unemployed in a city of people 25 years or older who are college graduates is given below, by year.

Year 2000 2002 2005 2007 2010
Percent Graduates 6.5 7.0 7.4 8.2 9.0
Table 5

Based on the set of data given in Table 7, calculate the regression line using a calculator or other technology tool, and determine the correlation coefficient to three decimal places.

x 10 12 15 18 20
y 36 34 30 28 22
Table 7

Answer

y= − 1.294x+ 49.412; r= − 0.974

2.R-43 §2.R source ↗

For the following exercises, consider this scenario: The population of a city increased steadily over a ten-year span. The following ordered pairs show the population and the year over the ten-year span (population, year) for specific recorded years:

(3,600, 2000); (4,000, 2001); (4,700, 2003); (6,000, 2006)

Predict when the population will hit 12,000.

Answer

Early in 2022

2.R-45 §2.R source ↗

For the following exercises, consider this scenario: The population of a city increased steadily over a ten-year span. The following ordered pairs show the population and the year over the ten-year span (population, year) for specific recorded years:

(3,600, 2000); (4,000, 2001); (4,700, 2003); (6,000, 2006)

According to the model, what is the population in 2014?

Answer

7,660

2.T-1 §2.T source ↗

Determine whether the following algebraic equation can be written as a linear function. 2x+3y=7

Answer

Yes.

2.T-3 §2.T source ↗

Determine whether the following function is increasing or decreasing. f(x)=7x+9

Answer

Increasing

2.T-5 §2.T source ↗

Given the following set of information, find a linear equation satisfying the conditions, if possible.

x intercept at (–4, 0) and y-intercept at (0, –6)

Answer

y=−1.5x−6

2.T-7 §2.T source ↗

Write an equation for line in Figure 2.

A Cartesian coordinate plane displays a straight line. The x-axis and y-axis both range from -6 to 6, with grid lines at integer intervals. The line passes through the origin (0,0) and has a negative slope of -2. It extends infinitely, passing through points such as (-2, 4) and (2, -4), and is represented by the equation y = -2x. Figure 2

Answer

y=−2x−1

2.T-9 §2.T source ↗

Does Table 2 represent a linear function? If so, find a linear equation that models the data.

x 1 3 7 11
g(x) 4 9 19 12
Table 2

Answer

No.

2.T-11 §2.T source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

y= 3 4 x−9 −4x−3y=8

Answer

Perpendicular

2.T-13 §2.T source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

Find the x- and y-intercepts of the equation 2x+7y=−14.

Answer

(−7,0); (0,−2)

2.T-15 §2.T source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

Write an equation for a line perpendicular to f(x)=4x+3 and passing through the point (8,10).

Answer

y=−0.25x+12

2.T-17 §2.T source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

Graph of the linear function f(x)=−x+6.

Answer

A coordinate plane with the x-axis labeled from -5 to 8 and the y-axis labeled from -2 to 7. A straight line is plotted, passing through the y-axis at the point (0, 6) and the x-axis at the point (6, 0). The line has a negative slope, decreasing from left to right, and extends infinitely in both directions.

2.T-19 §2.T source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

A car rental company offers two plans for renting a car.

• Plan A: $25 per day and $0.10 per mile

• Plan B: $40 per day with free unlimited mileage

How many miles would you need to drive for plan B to save you money?

Answer

150

2.T-21 §2.T source ↗

For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither parallel nor perpendicular:

A town’s population increases at a constant rate. In 2010 the population was 65,000. By 2012 the population had increased to 90,000. Assuming this trend continues, predict the population in 2018.

Answer

165,000

2.T-23 §2.T source ↗

For the following exercises, use the graph in Figure 3, showing the profit, y, in thousands of dollars, of a company in a given year, x, where x represents years since 1980.

A line graph in a coordinate plane displays a single blue line segment with a positive slope. The x-axis is labeled from 0 to 30 in increments of 5, and the y-axis is labeled from 0 to 35,000 in increments of 5,000. The line starts approximately at x=5, y=16,000 and extends to approximately x=25, y=31,000, illustrating a positive linear correlation between the two variables. Figure 3

Find the linear function y, where y depends on x, the number of years since 1980.

Answer

y= 875x+ 10, 675

2.T-25 §2.T source ↗

For the following exercises, use the graph in Figure 3, showing the profit, y, in thousands of dollars, of a company in a given year, x, where x represents years since 1980.

A line graph in a coordinate plane displays a single blue line segment with a positive slope. The x-axis is labeled from 0 to 30 in increments of 5, and the y-axis is labeled from 0 to 35,000 in increments of 5,000. The line starts approximately at x=5, y=16,000 and extends to approximately x=25, y=31,000, illustrating a positive linear correlation between the two variables. Figure 3

In 2004, a school population was 1250. By 2012 the population had dropped to 875. Assume the population is changing linearly.

ⓐ How much did the population drop between the year 2004 and 2012?

ⓑ What is the average population decline per year?

ⓒ Find an equation for the population, P, of the school t years after 2004.

Answer

a) 375; b) dropped an average of 46.875, or about 47 people per year; c) y= − 46.875t+ 1250

2.T-27 §2.T source ↗

For the following exercises, use the graph in Figure 3, showing the profit, y, in thousands of dollars, of a company in a given year, x, where x represents years since 1980.

A line graph in a coordinate plane displays a single blue line segment with a positive slope. The x-axis is labeled from 0 to 30 in increments of 5, and the y-axis is labeled from 0 to 35,000 in increments of 5,000. The line starts approximately at x=5, y=16,000 and extends to approximately x=25, y=31,000, illustrating a positive linear correlation between the two variables. Figure 3

Draw a best-fit line for the plotted data.

A scatter plot displaying five data points that show a general upward trend, indicating a positive correlation between the x and y variables.

Answer

This scatter plot displays several data points that exhibit a clear positive linear relationship. An orange line of best fit is drawn through the data, visually representing this trend. The x-axis is labeled 'x' and ranges from 0 to 12, while the y-axis is labeled 'y' and ranges from 0 to 35.

2.T-29 §2.T source ↗

For the following exercises, use Table 4, which shows the percent of unemployed persons 25 years or older who are college graduates in a particular city, by year.

Year 2000 2002 2005 2007 2010
Percent Graduates 8.5 8.0 7.2 6.7 6.4
Table 4

In what year will the percentage drop below 4%?

Answer

Early in 2018

2.T-31 §2.T source ↗

For the following exercises, consider this scenario: The population of a city increased steadily over a ten-year span. The following ordered pairs shows the population (in hundreds) and the year over the ten-year span, (population, year) for specific recorded years:

(4,500, 2000); (4,700, 2001); (5,200, 2003); (5,800, 2006)

Use linear regression to determine a function y, where the year depends on the population. Round to three decimal places of accuracy.

Answer

y= 0.00455x+ 1979.5

2.T-33 §2.T source ↗

For the following exercises, consider this scenario: The population of a city increased steadily over a ten-year span. The following ordered pairs shows the population (in hundreds) and the year over the ten-year span, (population, year) for specific recorded years:

(4,500, 2000); (4,700, 2001); (5,200, 2003); (5,800, 2006)

What is the correlation coefficient for this model?

Answer

r=0.999

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Problems and answers are adapted from Precalculus 2e by Jay Abramson, OpenStax, and are used under the CC BY-NC-SA 4.0 licence. Access for free at https://openstax.org/books/precalculus-2e/pages/1-introduction-to-functions. Illustrations: Copyright Rice University, OpenStax, under CC BY-NC-SA 4.0 license. This adaptation is released under the same licence, is non-commercial, and is neither affiliated with nor endorsed by OpenStax or Rice University.