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Chapter 5: Curve Sketching

65 problems · 0 figures

5.1.1 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

y=x2−x

Answer

min at x=1/2

5.1.2 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

y=2+3x−x3

Answer

min at x=−1⁠, max at x=1

5.1.3 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

y=x3−9x2+24x

Answer

max at x=2⁠, min at x=4

5.1.4 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

y=x4−2x2+3

Answer

min at x=±1⁠, max at x=0⁠.

5.1.5 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

y=3x4−4x3

Answer

min at x=1

5.1.6 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

y=(x2−1)/x

Answer

none

5.1.7 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

y=3x2−(1/x2)

Answer

none

5.1.8 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

y=cos⁡(2x)−x

Answer

min at x=7π/12+kπ⁠, max at x=−π/12+kπ⁠, for integer k⁠.

5.1.9 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

f(x)={x−1x<2x2x≥2

Answer

none

5.1.10 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

f(x)={x−3x5

Answer

local max at x=5

5.1.11 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

f(x)=x2−98x+4

Answer

local min at x=49

5.1.12 §5.1 source ↗

Find all local maximum and minimum points (x,y) by the method of this section.

f(x)={−2x=01/x2x≠0

Answer

local min at x=0

5.1.13 §5.1 source ↗

Find the local extrema of f(x)=|x|+|x−1|⁠.

Answer

Local min of 1 at every point of [0,1]⁠, local max of 1 at every point of (0,1)⁠.

5.1.16 §5.1 source ↗

How many critical points can a quadratic polynomial function have?

Answer

one

5.2.1 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

y=x2−x

Answer

min at x=1/2

5.2.2 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

y=2+3x−x3

Answer

min at x=−1⁠, max at x=1

5.2.3 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

y=x3−9x2+24x

Answer

max at x=2⁠, min at x=4

5.2.4 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

y=x4−2x2+3

Answer

min at x=±1⁠, max at x=0⁠.

5.2.5 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

y=3x4−4x3

Answer

min at x=1

5.2.6 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

y=(x2−1)/x

Answer

none

5.2.7 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

y=3x2−(1/x2)

Answer

none

5.2.8 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

y=cos⁡(2x)−x

Answer

min at x=7π/12+kπ⁠, max at x=−π/12+kπ⁠, for integer k⁠.

5.2.9 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

f(x)=(5−x)/(x+2)

Answer

none

5.2.10 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

f(x)=|x2−121|

Answer

max at x=0⁠, min at x=±11

5.2.11 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

f(x)=x3/(x+1)

Answer

min at x=−3/2⁠, neither at x=0

5.2.13 §5.2 source ↗

Find all critical points and identify them as local maximum points, local minimum points, or neither.

f(x)=sin2⁡x

Answer

min at nπ⁠, max at π/2+nπ

5.2.14 §5.2 source ↗

Find the maxima and minima of f(x)=sec⁡x⁠.

Answer

min at 2nπ⁠, max at (2n+1)π

5.2.15 §5.2 source ↗

Let f(θ)=cos2⁡(θ)−2sin⁡(θ)⁠. Find the intervals where f is increasing and the intervals where f is decreasing in [0,2π]⁠. Use this information to classify the critical points of f as either local maximums, local minimums, or neither.

Answer

min at π/2+2nπ⁠, max at 3π/2+2nπ

5.3.1 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=x2−x

Answer

min at x=1/2

5.3.2 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=2+3x−x3

Answer

min at x=−1⁠, max at x=1

5.3.3 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=x3−9x2+24x

Answer

max at x=2⁠, min at x=4

5.3.4 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=x4−2x2+3

Answer

min at x=±1⁠, max at x=0⁠.

5.3.5 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=3x4−4x3

Answer

min at x=1

5.3.6 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=(x2−1)/x

Answer

none

5.3.7 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=3x2−(1/x2)

Answer

none

5.3.8 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=cos⁡(2x)−x

Answer

min at x=7π/12+nπ⁠, max at x=−π/12+nπ⁠, for integer n⁠.

5.3.9 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=4x+1−x

Answer

max at x=63/64

5.3.10 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=(x+1)/5x2+35

Answer

max at x=7

5.3.11 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=x5−x

Answer

max at −5−1/4⁠, min at 5−1/4

5.3.12 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=6x+sin⁡3x

Answer

none

5.3.13 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=x+1/x

Answer

max at −1⁠, min at 1

5.3.14 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=x2+1/x

Answer

min at 2−1/3

5.3.15 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=(x+5)1/4

Answer

none

5.3.16 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=tan2⁡x

Answer

min at nπ

5.3.17 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=cos2⁡x−sin2⁡x

Answer

max at nπ⁠, min at π/2+nπ

5.3.18 §5.3 source ↗

Find all local maximum and minimum points by the second derivative test, when possible. (You need only find the points identified by the second derivative test; ignore any others.)

y=sin3⁡x

Answer

max at π/2+2nπ⁠, min at 3π/2+2nπ

5.4.1 §5.4 source ↗

Describe the concavity of the functions.

y=x2−x

Answer

concave up everywhere

5.4.2 §5.4 source ↗

Describe the concavity of the functions.

y=2+3x−x3

Answer

concave up when x<0⁠, concave down when x>0

5.4.3 §5.4 source ↗

Describe the concavity of the functions.

y=x3−9x2+24x

Answer

concave down when x<3⁠, concave up when x>3

5.4.4 §5.4 source ↗

Describe the concavity of the functions.

y=x4−2x2+3

Answer

concave up when x<−1/3 or x>1/3⁠, concave down when −1/3<x<1/3

5.4.5 §5.4 source ↗

Describe the concavity of the functions.

y=3x4−4x3

Answer

concave up when x<0 or x>2/3⁠, concave down when 0<x<2/3

5.4.6 §5.4 source ↗

Describe the concavity of the functions.

y=(x2−1)/x

Answer

concave up when x<0⁠, concave down when x>0

5.4.7 §5.4 source ↗

Describe the concavity of the functions.

y=3x2−(1/x2)

Answer

concave up when x<−1 or x>1⁠, concave down when −1<x<0 or 0<x<1

5.4.8 §5.4 source ↗

Describe the concavity of the functions.

y=sin⁡x+cos⁡x

Answer

concave down on ((8n−1)π/4,(8n+3)π/4)⁠, concave up on ((8n+3)π/4,(8n+7)π/4)⁠, for integer n

5.4.9 §5.4 source ↗

Describe the concavity of the functions.

y=4x+1−x

Answer

concave down everywhere

5.4.10 §5.4 source ↗

Describe the concavity of the functions.

y=(x+1)/5x2+35

Answer

concave up on (−∞,(21−497)/4) and (21+497)/4,∞)

5.4.11 §5.4 source ↗

Describe the concavity of the functions.

y=x5−x

Answer

concave up on (0,∞)

5.4.12 §5.4 source ↗

Describe the concavity of the functions.

y=6x+sin⁡3x

Answer

concave down on (2nπ/3,(2n+1)π/3)

5.4.13 §5.4 source ↗

Describe the concavity of the functions.

y=x+1/x

Answer

concave up on (0,∞)

5.4.14 §5.4 source ↗

Describe the concavity of the functions.

y=x2+1/x

Answer

concave up on (−∞,−1) and (0,∞)

5.4.15 §5.4 source ↗

Describe the concavity of the functions.

y=(x+5)1/4

Answer

concave down everywhere

5.4.16 §5.4 source ↗

Describe the concavity of the functions.

y=tan2⁡x

Answer

concave up everywhere

5.4.17 §5.4 source ↗

Describe the concavity of the functions.

y=cos2⁡x−sin2⁡x

Answer

concave up on (π/4+nπ,3π/4+nπ)

5.4.18 §5.4 source ↗

Describe the concavity of the functions.

y=sin3⁡x

Answer

inflection points at nπ⁠, ±arcsin⁡(2/3)+nπ

5.4.19 §5.4 source ↗

Identify the intervals on which the graph of the function f(x)=x4−4x3+10 is of one of these four shapes: concave up and increasing; concave up and decreasing; concave down and increasing; concave down and decreasing.

Answer

up/incr: (3,∞)⁠, up/decr: (−∞,0)⁠, (2,3)⁠, down/decr: (0,2)

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Exercises and answers are adapted from Calculus: Early Transcendentals by David Guichard and friends, which is free to read and download, and are used under the CC BY-NC-SA 4.0 licence. They are taken from the book’s online edition and set for the web, so they may differ slightly from the printed page. This adaptation is released under the same licence and is neither affiliated with nor endorsed by David Guichard or Whitman College. The book was first written by David Guichard. Its chapters 1–9 modify and expand notes by Neal Koblitz of the University of Washington; it includes exercises and examples from H. Jerome Keisler’s Elementary Calculus: An Approach Using Infinitesimals, from which its chapter on differential equations is largely derived, and some exercises from the OpenStax Calculus books; and Albert Schueller, Barry Balof and Mike Wills contributed additional material.