Calculus Final Exam
Complete Derivatives Review Worksheet

Mixed: Beginner–Advanced ⌛ Est. 3–4 Hours 60 Problems

This comprehensive final exam review covers every major derivative topic — from basic power rules through chain rule, product and quotient rules, to real-world optimization and related rates. Problems are sequenced by section and difficulty. Full step-by-step solutions are included. Ideal for AP Calculus AB/BC final exam preparation, college Calculus I, and comprehensive review.

Learning Objectives

  • Apply the power, constant, sum, and difference rules to differentiate polynomial, radical, and rational functions.
  • Use the chain rule to differentiate composite functions involving trigonometric, exponential, and logarithmic expressions.
  • Combine the product rule and quotient rule correctly with other differentiation rules.
  • Find critical points and classify extrema using the first and second derivative tests.
  • Set up and solve optimization and related-rates problems from real-world contexts.

Key Derivative Rules — Quick Reference

Use this reference as needed during the review. On your actual exam, these formulas must be memorized.

Core Differentiation Rules

Power Rule: \(\dfrac{d}{dx}[x^n] = nx^{n-1}\)

Chain Rule: \(\dfrac{d}{dx}[f(g(x))] = f'(g(x))\cdot g'(x)\)

Product Rule: \(\dfrac{d}{dx}[f\cdot g] = f'g + fg'\)

Quotient Rule: \(\dfrac{d}{dx}\!\left[\dfrac{f}{g}\right] = \dfrac{f'g - fg'}{g^2}\)

FunctionDerivativeFunctionDerivative
\(\sin x\)\(\cos x\)\(e^x\)\(e^x\)
\(\cos x\)\(-\sin x\)\(a^x\)\(a^x \ln a\)
\(\tan x\)\(\sec^2 x\)\(\ln x\)\(1/x\)
\(\sec x\)\(\sec x\tan x\)\(\log_a x\)\(1/(x\ln a)\)
\(\csc x\)\(-\csc x\cot x\)\(\arcsin x\)\(1/\sqrt{1-x^2}\)
\(\cot x\)\(-\csc^2 x\)\(\arctan x\)\(1/(1+x^2)\)

Section A — Basic Differentiation (Problems 1–15)

Beginner

Apply the power rule, constant multiple rule, sum and difference rules, and basic trig/exponential/log derivatives. No chain, product, or quotient rule needed.

  1. Find \(f'(x)\) if \(f(x) = 7x^4 - 3x^2 + 5x - 9\).
  2. Differentiate \(g(x) = \sqrt[3]{x^4} - \dfrac{2}{x^3}\).
  3. Find \(\dfrac{d}{dx}\!\left[\dfrac{x^5 - 4x^3 + 7}{x^2}\right]\) by simplifying first.
  4. Find \(h'(t)\) if \(h(t) = 6e^t - 4\ln t + 3\).
  5. Differentiate \(y = 5\sin x - 2\cos x + \tan x\).
  6. Find \(f'(x)\) if \(f(x) = 8x^{3/4} - 12x^{1/2} + x^{-2}\).
  7. Differentiate \(y = 3\sec x - \cot x + 2\).
  8. Find the derivative of \(f(x) = (2x-3)^2\) by expanding first.
  9. Find \(f'(x)\) if \(f(x) = \pi x^3 - e x + \pi^2\). (Treat \(\pi\) and \(e\) as constants.)
  10. Differentiate \(y = 4\ln x + 7e^x - 2^x\).
  11. Find \(\dfrac{ds}{dt}\) if \(s(t) = 16t^2 - v_0 t + s_0\). (Treat \(v_0\) and \(s_0\) as constants.)
  12. Find the slope of the tangent line to \(f(x) = x^3 - 5x + 2\) at \(x = 2\).
  13. Differentiate \(y = \arctan x - \arcsin x\).
  14. Find \(f'(x)\) if \(f(x) = \dfrac{3}{x^4} + \dfrac{5}{\sqrt{x}} - 6x\).
  15. Find the equation of the tangent line to \(y = \ln x + e^x\) at \(x = 1\).

Section B — Chain Rule (Problems 16–30)

Intermediate

All problems require the chain rule. Some combine it with basic rules. Identify the outer and inner function before differentiating.

  1. Differentiate \(y = (3x^2 - 5x + 1)^6\).
  2. Find \(f'(x)\) if \(f(x) = \sin(4x^3 - x)\).
  3. Differentiate \(g(t) = e^{t^2 - 3t}\).
  4. Find \(\dfrac{dy}{dx}\) for \(y = \ln(x^2 + 9)\).
  5. Differentiate \(y = \cos^5(x)\). (Rewrite as \([\cos x]^5\).)
  6. Find \(f'(x)\) if \(f(x) = \sqrt{5x^2 - 2x + 3}\).
  7. Differentiate \(y = \tan(e^x)\).
  8. Find \(\dfrac{d}{dt}\!\left[\ln(\sin t)\right]\).
  9. Differentiate \(y = e^{\cos x}\).
  10. Find \(f'(x)\) if \(f(x) = \sec(3x^2)\).
  11. Differentiate \(y = \arctan(2x^3)\).
  12. Find \(\dfrac{dy}{dx}\) for \(y = \left(\dfrac{x-1}{x+1}\right)^4\). (Use chain rule; quotient is the inner function.)
  13. Differentiate \(y = \ln|\sec x + \tan x|\).
  14. Find \(f'(x)\) if \(f(x) = e^{\sqrt{x^2+1}}\).
  15. Differentiate \(y = \sin^2(3x) + \cos^2(3x)\). State the answer without computing (explain why).

Section C — Product & Quotient Rules (Problems 31–45)

Intermediate

Each problem requires the product rule, the quotient rule, or both — often combined with the chain rule. Simplify answers where possible.

  1. Differentiate \(y = x^3 \sin x\).
  2. Find \(f'(x)\) if \(f(x) = e^x(x^2 - 4x + 1)\).
  3. Differentiate \(y = \sqrt{x}\,\ln x\).
  4. Find \(g'(t)\) if \(g(t) = t^2 e^{-t}\).
  5. Differentiate \(y = x\cos x\sin x\). (Three-factor product rule.)
  6. Find \(f'(x)\) if \(f(x) = \dfrac{x^2 + 3x}{x - 5}\).
  7. Differentiate \(y = \dfrac{\sin x}{x^2}\).
  8. Find \(h'(x)\) if \(h(x) = \dfrac{e^x}{x^3 + 1}\).
  9. Differentiate \(y = \dfrac{\ln x}{\sqrt{x}}\).
  10. Find \(f'(x)\) if \(f(x) = \dfrac{x^2 - 1}{x^2 + 1}\).
  11. Differentiate \(y = x^2\arctan x\).
  12. Find \(f'(x)\) if \(f(x) = e^x\cos x\). Then find \(f''(x)\).
  13. Differentiate \(y = \dfrac{\tan x}{1 + x^2}\).
  14. Given \(p(x) = f(x)\cdot g(x)\), with \(f(2)=3,\;f'(2)=-1,\;g(2)=5,\;g'(2)=4\), find \(p'(2)\).
  15. Given \(q(x) = \dfrac{f(x)}{g(x)}\) with the values from Problem 44, find \(q'(2)\).

Section D — Applications of Derivatives (Problems 46–60)

Advanced

This section covers optimization (max/min), related rates, increasing/decreasing intervals, concavity, and linearization. Show all work and include units where applicable.

  1. Increasing/Decreasing. For \(f(x)=x^3-6x^2+9x-4\), find all critical points and determine intervals where \(f\) is increasing or decreasing.
  2. Second Derivative Test. For \(f(x)=2x^3-9x^2+12x+1\), find all local maxima and minima using the second derivative test.
  3. Absolute Extrema. Find the absolute maximum and minimum values of \(f(x)=x^4-4x^3+4x^2\) on \([-1,3]\).
  4. Concavity & Inflection. Find all inflection points and intervals of concavity for \(f(x)=x^4-8x^2+3\).
  5. Linearization. Find the linear approximation \(L(x)\) to \(f(x)=\sqrt{x}\) at \(a=25\). Use it to estimate \(\sqrt{26}\).
  6. Optimization. A farmer has 200 m of fencing and wants to enclose a rectangular field along a river (no fence on the river side). Find the dimensions that maximize the area.
  7. Optimization. Find two positive numbers whose sum is 50 and whose product is as large as possible.
  8. Optimization. A box with a square base and open top must have a volume of \(32\,\text{m}^3\). Find the dimensions that minimize the surface area.
  9. Optimization. A ladder 10 m long leans against a vertical wall. Find the point where the ladder touches the ground that minimizes the area of the triangle formed by the ladder, wall, and ground. (\textit{Hint: maximize area, find critical point.})
  10. Related Rates. A spherical balloon is being inflated. When the radius is 5 cm, the radius is increasing at 2 cm/s. Find the rate at which the volume is increasing at that moment. (\(V=\frac{4}{3}\pi r^3\).)
  11. Related Rates. A 10-ft ladder rests against a vertical wall. The bottom slides away at 2 ft/s. How fast is the top sliding down when the bottom is 6 ft from the wall?
  12. Related Rates. Water drains from a conical tank (vertex down) with radius 4 m and height 8 m at \(2\,\text{m}^3/\text{min}\). Find \(dh/dt\) when \(h = 4\,\text{m}\). (\(V=\frac{1}{3}\pi r^2 h\).)
  13. Related Rates. Two cars leave an intersection at the same time. Car A travels north at 60 mph; Car B travels east at 80 mph. How fast is the distance between them increasing after 1 hour?
  14. Mean Value Theorem. Verify that \(f(x)=x^3-x\) satisfies the conditions of the MVT on \([0,2]\). Find all values of \(c\) guaranteed by the theorem.
  15. Applied Rate of Change. A company's profit is \(P(x)=-0.02x^2+120x-1500\) dollars, where \(x\) is units sold. Find the marginal profit at \(x=2000\) and determine if production should be increased or decreased. Interpret your answer.

Answer Key with Step-by-Step Solutions

Section A — Basic Differentiation (Problems 1–15)

1

Apply the power rule to each term: \(\frac{d}{dx}[7x^4]=28x^3\), \(\frac{d}{dx}[-3x^2]=-6x\), \(\frac{d}{dx}[5x]=5\), \(\frac{d}{dx}[-9]=0\).

\(f'(x)=28x^3-6x+5\)
2

Rewrite: \(g(x)=x^{4/3}-2x^{-3}\). Differentiate: \(g'(x)=\frac{4}{3}x^{1/3} - 2(-3)x^{-4} = \frac{4}{3}x^{1/3}+6x^{-4}\).

\(g'(x)=\dfrac{4}{3}\sqrt[3]{x}+\dfrac{6}{x^4}\)
3

Divide: \(y = x^3 - 4x + 7x^{-2}\). Then \(y'=3x^2 - 4 + 7(-2)x^{-3} = 3x^2-4-\frac{14}{x^3}\).

\(y'=3x^2-4-\dfrac{14}{x^3}\)
4

\(\frac{d}{dt}[6e^t]=6e^t\); \(\frac{d}{dt}[-4\ln t]=-4/t\); \(\frac{d}{dt}[3]=0\).

\(h'(t)=6e^t-\dfrac{4}{t}\)
5

Term by term: \(\frac{d}{dx}[5\sin x]=5\cos x\); \(\frac{d}{dx}[-2\cos x]=2\sin x\); \(\frac{d}{dx}[\tan x]=\sec^2 x\).

\(y'=5\cos x+2\sin x+\sec^2 x\)
6

Power rule: \(\frac{d}{dx}[8x^{3/4}]=8\cdot\frac{3}{4}x^{-1/4}=6x^{-1/4}\); \(\frac{d}{dx}[-12x^{1/2}]=-6x^{-1/2}\); \(\frac{d}{dx}[x^{-2}]=-2x^{-3}\).

\(f'(x)=\dfrac{6}{x^{1/4}}-\dfrac{6}{\sqrt{x}}-\dfrac{2}{x^3}\)
7

\(\frac{d}{dx}[3\sec x]=3\sec x\tan x\); \(\frac{d}{dx}[-\cot x]=\csc^2 x\); \(\frac{d}{dx}[2]=0\).

\(y'=3\sec x\tan x+\csc^2 x\)
8

Expand: \((2x-3)^2=4x^2-12x+9\). Differentiate: \(y'=8x-12\).

\(f'(x)=8x-12\)
9

\(\pi\) and \(e\) are constants. \(f'(x)=3\pi x^2 - e\). (\(\pi^2\) is a constant; its derivative is 0.)

\(f'(x)=3\pi x^2 - e\)
10

\(\frac{d}{dx}[4\ln x]=4/x\); \(\frac{d}{dx}[7e^x]=7e^x\); \(\frac{d}{dx}[2^x]=2^x\ln 2\).

\(y'=\dfrac{4}{x}+7e^x+2^x\ln 2\)
11

\(v_0\) and \(s_0\) are constants. \(\frac{ds}{dt}=32t-v_0\). This is the velocity in free-fall kinematics.

\(\dfrac{ds}{dt}=32t-v_0\)
12

\(f'(x)=3x^2-5\). At \(x=2\): \(f'(2)=3(4)-5=7\).

Slope \(=7\)
13

\(\frac{d}{dx}[\arctan x]=\frac{1}{1+x^2}\); \(\frac{d}{dx}[-\arcsin x]=-\frac{1}{\sqrt{1-x^2}}\).

\(y'=\dfrac{1}{1+x^2}-\dfrac{1}{\sqrt{1-x^2}}\)
14

Rewrite: \(f(x)=3x^{-4}+5x^{-1/2}-6x\). Then \(f'(x)=-12x^{-5}-\frac{5}{2}x^{-3/2}-6\).

\(f'(x)=-\dfrac{12}{x^5}-\dfrac{5}{2x^{3/2}}-6\)
15

\(y'=\frac{1}{x}+e^x\). At \(x=1\): point \((1, 0+e)=(1,e)\), slope \(y'(1)=1+e\). Tangent: \(y-e=(1+e)(x-1)\), i.e. \(y=(1+e)x-1\).

\(y=(1+e)x-1\)

Section B — Chain Rule (Problems 16–30)

16

Outer: \(u^6\), inner: \(u=3x^2-5x+1\). \(y'=6(3x^2-5x+1)^5\cdot(6x-5)\).

\(y'=6(6x-5)(3x^2-5x+1)^5\)
17

Outer: \(\sin u\), inner: \(u=4x^3-x\). \(f'(x)=\cos(4x^3-x)\cdot(12x^2-1)\).

\(f'(x)=(12x^2-1)\cos(4x^3-x)\)
18

Outer: \(e^u\), inner: \(u=t^2-3t\). \(g'(t)=e^{t^2-3t}\cdot(2t-3)\).

\(g'(t)=(2t-3)e^{t^2-3t}\)
19

Outer: \(\ln u\), inner: \(u=x^2+9\). \(y'=\dfrac{1}{x^2+9}\cdot 2x=\dfrac{2x}{x^2+9}\).

\(y'=\dfrac{2x}{x^2+9}\)
20

Write \(y=(\cos x)^5\). Outer: \(u^5\), inner: \(\cos x\). \(y'=5\cos^4 x\cdot(-\sin x)=-5\cos^4 x\sin x\).

\(y'=-5\cos^4 x\sin x\)
21

Write \(y=(5x^2-2x+3)^{1/2}\). \(y'=\dfrac{1}{2}(5x^2-2x+3)^{-1/2}\cdot(10x-2)=\dfrac{10x-2}{2\sqrt{5x^2-2x+3}}\).

\(y'=\dfrac{5x-1}{\sqrt{5x^2-2x+3}}\)
22

Outer: \(\tan u\), inner: \(u=e^x\). \(y'=\sec^2(e^x)\cdot e^x=e^x\sec^2(e^x)\).

\(y'=e^x\sec^2(e^x)\)
23

Outer: \(\ln u\), inner: \(u=\sin t\). \(\dfrac{d}{dt}[\ln(\sin t)]=\dfrac{\cos t}{\sin t}=\cot t\).

\(y'=\cot t\)
24

Outer: \(e^u\), inner: \(u=\cos x\). \(y'=e^{\cos x}\cdot(-\sin x)=-\sin x\,e^{\cos x}\).

\(y'=-\sin x\,e^{\cos x}\)
25

Outer: \(\sec u\), inner: \(u=3x^2\). \(f'(x)=\sec(3x^2)\tan(3x^2)\cdot 6x=6x\sec(3x^2)\tan(3x^2)\).

\(f'(x)=6x\sec(3x^2)\tan(3x^2)\)
26

Outer: \(\arctan u\), inner: \(u=2x^3\). \(y'=\dfrac{1}{1+(2x^3)^2}\cdot 6x^2=\dfrac{6x^2}{1+4x^6}\).

\(y'=\dfrac{6x^2}{1+4x^6}\)
27

Let \(u=\dfrac{x-1}{x+1}\). By quotient rule: \(u'=\dfrac{(x+1)-(x-1)}{(x+1)^2}=\dfrac{2}{(x+1)^2}\). Then \(y'=4u^3\cdot u'=4\!\left(\dfrac{x-1}{x+1}\right)^3\!\cdot\dfrac{2}{(x+1)^2}=\dfrac{8(x-1)^3}{(x+1)^5}\).

\(y'=\dfrac{8(x-1)^3}{(x+1)^5}\)
28

Let \(u=\sec x+\tan x\). \(u'=\sec x\tan x+\sec^2 x=\sec x(\tan x+\sec x)\). So \(y'=\dfrac{\sec x(\sec x+\tan x)}{\sec x+\tan x}=\sec x\).

\(y'=\sec x\)
29

Let \(v=\sqrt{x^2+1}=(x^2+1)^{1/2}\). Then \(v'=\dfrac{x}{\sqrt{x^2+1}}\). By chain rule on \(e^v\): \(y'=e^{\sqrt{x^2+1}}\cdot\dfrac{x}{\sqrt{x^2+1}}\).

\(y'=\dfrac{xe^{\sqrt{x^2+1}}}{\sqrt{x^2+1}}\)
30

By the Pythagorean identity, \(\sin^2(3x)+\cos^2(3x)=1\) for all \(x\). The derivative of a constant is 0.

\(y'=0\)

Section C — Product & Quotient Rules (Problems 31–45)

31

Let \(f=x^3, f'=3x^2\); \(g=\sin x, g'=\cos x\). Product rule: \(y'=3x^2\sin x + x^3\cos x\).

\(y'=3x^2\sin x+x^3\cos x\)
32

\(f=e^x, f'=e^x\); \(g=x^2-4x+1, g'=2x-4\). Product: \(f'(x)=e^x(x^2-4x+1)+e^x(2x-4)=e^x(x^2-2x-3)=e^x(x-3)(x+1)\).

\(f'(x)=e^x(x^2-2x-3)\)
33

\(f=x^{1/2},f'=\frac{1}{2}x^{-1/2}\); \(g=\ln x, g'=\frac{1}{x}\). Product: \(y'=\frac{\ln x}{2\sqrt{x}}+\frac{\sqrt{x}}{x}=\frac{\ln x}{2\sqrt{x}}+\frac{1}{\sqrt{x}}=\frac{\ln x+2}{2\sqrt{x}}\).

\(y'=\dfrac{\ln x+2}{2\sqrt{x}}\)
34

\(f=t^2,f'=2t\); \(g=e^{-t},g'=-e^{-t}\). Product: \(g'(t)=2te^{-t}-t^2e^{-t}=te^{-t}(2-t)\).

\(g'(t)=te^{-t}(2-t)\)
35

Three-factor product: \((fgh)'=f'gh+fg'h+fgh'\) where \(f=x,g=\cos x,h=\sin x\). \(f'=1,g'=-\sin x,h'=\cos x\). So \(y'=\cos x\sin x + x(-\sin x)\sin x + x\cos x\cos x = \cos x\sin x - x\sin^2 x + x\cos^2 x\). Simplify: \(=\cos x\sin x + x(\cos^2 x-\sin^2 x)=\frac{1}{2}\sin 2x + x\cos 2x\).

\(y'=\tfrac{1}{2}\sin 2x+x\cos 2x\)
36

Quotient: \(f=x^2+3x,f'=2x+3\); \(g=x-5,g'=1\). \(y'=\dfrac{(2x+3)(x-5)-(x^2+3x)}{(x-5)^2}=\dfrac{2x^2-7x-15-x^2-3x}{(x-5)^2}=\dfrac{x^2-10x-15}{(x-5)^2}\).

\(f'(x)=\dfrac{x^2-10x-15}{(x-5)^2}\)
37

\(f=\sin x,f'=\cos x\); \(g=x^2,g'=2x\). Quotient: \(y'=\dfrac{x^2\cos x-2x\sin x}{x^4}=\dfrac{x\cos x-2\sin x}{x^3}\).

\(y'=\dfrac{x\cos x-2\sin x}{x^3}\)
38

\(f=e^x,f'=e^x\); \(g=x^3+1,g'=3x^2\). Quotient: \(h'(x)=\dfrac{e^x(x^3+1)-e^x(3x^2)}{(x^3+1)^2}=\dfrac{e^x(x^3-3x^2+1)}{(x^3+1)^2}\).

\(h'(x)=\dfrac{e^x(x^3-3x^2+1)}{(x^3+1)^2}\)
39

\(f=\ln x,f'=1/x\); \(g=x^{1/2},g'=\frac{1}{2}x^{-1/2}\). Quotient: \(y'=\dfrac{\frac{1}{x}\cdot\sqrt{x}-\ln x\cdot\frac{1}{2\sqrt{x}}}{x}=\dfrac{\frac{1}{\sqrt{x}}-\frac{\ln x}{2\sqrt{x}}}{x}=\dfrac{2-\ln x}{2x^{3/2}}\).

\(y'=\dfrac{2-\ln x}{2x^{3/2}}\)
40

\(f=x^2-1,f'=2x\); \(g=x^2+1,g'=2x\). Quotient: \(f'(x)=\dfrac{2x(x^2+1)-2x(x^2-1)}{(x^2+1)^2}=\dfrac{2x(x^2+1-x^2+1)}{(x^2+1)^2}=\dfrac{4x}{(x^2+1)^2}\).

\(f'(x)=\dfrac{4x}{(x^2+1)^2}\)
41

\(f=x^2,f'=2x\); \(g=\arctan x,g'=\frac{1}{1+x^2}\). Product: \(y'=2x\arctan x+\dfrac{x^2}{1+x^2}\).

\(y'=2x\arctan x+\dfrac{x^2}{1+x^2}\)
42

\(f'(x)=e^x\cos x+e^x(-\sin x)=e^x(\cos x-\sin x)\). For \(f''(x)\): product rule again: \(f''(x)=e^x(\cos x-\sin x)+e^x(-\sin x-\cos x)=e^x(\cos x-\sin x-\sin x-\cos x)=-2e^x\sin x\).

\(f'(x)=e^x(\cos x-\sin x);\quad f''(x)=-2e^x\sin x\)
43

\(f=\tan x,f'=\sec^2 x\); \(g=1+x^2,g'=2x\). Quotient: \(y'=\dfrac{\sec^2 x(1+x^2)-2x\tan x}{(1+x^2)^2}\).

\(y'=\dfrac{(1+x^2)\sec^2 x-2x\tan x}{(1+x^2)^2}\)
44

Product rule: \(p'(x)=f'(x)g(x)+f(x)g'(x)\). At \(x=2\): \(p'(2)=(-1)(5)+(3)(4)=-5+12=7\).

\(p'(2)=7\)
45

Quotient rule: \(q'(x)=\dfrac{f'(x)g(x)-f(x)g'(x)}{[g(x)]^2}\). At \(x=2\): \(q'(2)=\dfrac{(-1)(5)-(3)(4)}{5^2}=\dfrac{-5-12}{25}=\dfrac{-17}{25}\).

\(q'(2)=-\dfrac{17}{25}\)

Section D — Applications of Derivatives (Problems 46–60)

46

\(f'(x)=3x^2-12x+9=3(x^2-4x+3)=3(x-1)(x-3)\). Critical points: \(x=1\) and \(x=3\). Sign of \(f'\): positive on \((-\infty,1)\), negative on \((1,3)\), positive on \((3,\infty)\).

Increasing on \((-\infty,1)\cup(3,\infty)\); decreasing on \((1,3)\). Local max at \(x=1\), local min at \(x=3\).
47

\(f'(x)=6x^2-18x+12=6(x-1)(x-2)\). Critical points: \(x=1,x=2\). \(f''(x)=12x-18\). \(f''(1)=-6<0\) → local max; \(f''(2)=6>0\) → local min. Values: \(f(1)=2-9+12+1=6\); \(f(2)=16-36+24+1=5\).

Local max at \((1,6)\); local min at \((2,5)\).
48

\(f'(x)=4x^3-12x^2+8x=4x(x-1)(x-2)\). Critical points in \([-1,3]\): \(x=0,1,2\). Evaluate: \(f(-1)=1+4+4=9\); \(f(0)=0\); \(f(1)=1-4+4=1\); \(f(2)=16-32+16=0\); \(f(3)=81-108+36=9\).

Absolute max \(=9\) at \(x=-1\) and \(x=3\); absolute min \(=0\) at \(x=0\) and \(x=2\).
49

\(f''(x)=12x^2-16\). Set \(f''(x)=0\): \(x^2=\frac{4}{3}\Rightarrow x=\pm\frac{2}{\sqrt{3}}\). Check sign changes: \(f''<0\) on \(\!\left(-\frac{2}{\sqrt{3}},\frac{2}{\sqrt{3}}\right)\) (concave down), \(f''>0\) outside (concave up). Inflection points at \(x=\pm\frac{2\sqrt{3}}{3}\).

Inflection at \(x=\pm\dfrac{2\sqrt{3}}{3}\approx\pm1.155\). Concave up on \((-\infty,-\tfrac{2\sqrt{3}}{3})\cup(\tfrac{2\sqrt{3}}{3},\infty)\).
50

\(f'(x)=\frac{1}{2\sqrt{x}}\). At \(a=25\): \(f(25)=5\), \(f'(25)=\frac{1}{10}\). \(L(x)=5+\frac{1}{10}(x-25)\). Estimate: \(L(26)=5+\frac{1}{10}(1)=5.1\). (True value: \(\sqrt{26}\approx5.099\).)

\(L(x)=5+\tfrac{1}{10}(x-25)\); \(\sqrt{26}\approx5.1\)
51

Let width \(= x\) (two sides), length \(= y\) (one side parallel to river). Constraint: \(2x+y=200\Rightarrow y=200-2x\). Area: \(A=xy=x(200-2x)=200x-2x^2\). \(\frac{dA}{dx}=200-4x=0\Rightarrow x=50\,\text{m}\), \(y=100\,\text{m}\). Second derivative \(-4<0\) confirms maximum.

Dimensions: \(50\,\text{m}\times100\,\text{m}\); maximum area \(=5000\,\text{m}^2\).
52

Let numbers be \(x\) and \(50-x\). Product \(P=x(50-x)=50x-x^2\). \(P'=50-2x=0\Rightarrow x=25\). Both numbers are 25; \(P''=-2<0\) confirms maximum.

Both numbers are \(25\); maximum product \(=625\).
53

Let side of square base \(=x\), height \(=h\). Volume: \(x^2 h=32\Rightarrow h=32/x^2\). Surface area (open top): \(S=x^2+4xh=x^2+\frac{128}{x}\). \(\frac{dS}{dx}=2x-\frac{128}{x^2}=0\Rightarrow x^3=64\Rightarrow x=4\,\text{m}\). Then \(h=32/16=2\,\text{m}\).

Base \(4\,\text{m}\times4\,\text{m}\), height \(2\,\text{m}\); minimum surface area \(=48\,\text{m}^2\).
54

Let the foot of the ladder be at distance \(x\) from the wall, so the height is \(y=\sqrt{100-x^2}\). The area of the triangle is \(A=\frac{1}{2}xy=\frac{1}{2}x\sqrt{100-x^2}\). Set \(\frac{dA}{dx}=0\): \(\frac{dA}{dx}=\frac{1}{2}\!\left[\sqrt{100-x^2}+x\cdot\frac{-x}{\sqrt{100-x^2}}\right]=\frac{100-2x^2}{2\sqrt{100-x^2}}=0\Rightarrow x^2=50\Rightarrow x=5\sqrt{2}\,\text{m}\). Height \(=5\sqrt{2}\,\text{m}\).

Foot at \(x=5\sqrt{2}\approx7.07\,\text{m}\); maximum triangle area \(=25\,\text{m}^2\).
55

\(V=\frac{4}{3}\pi r^3\Rightarrow\frac{dV}{dt}=4\pi r^2\frac{dr}{dt}\). At \(r=5,\frac{dr}{dt}=2\): \(\frac{dV}{dt}=4\pi(25)(2)=200\pi\,\text{cm}^3/\text{s}\).

\(\dfrac{dV}{dt}=200\pi\approx628.3\,\text{cm}^3/\text{s}\)
56

Pythagorean relation: \(x^2+y^2=100\). Differentiate: \(2x\frac{dx}{dt}+2y\frac{dy}{dt}=0\Rightarrow\frac{dy}{dt}=-\frac{x}{y}\frac{dx}{dt}\). When \(x=6\): \(y=\sqrt{100-36}=8\). With \(\frac{dx}{dt}=2\): \(\frac{dy}{dt}=-\frac{6}{8}(2)=-\frac{3}{2}\,\text{ft/s}\).

\(\dfrac{dy}{dt}=-\dfrac{3}{2}\,\text{ft/s}\) (sliding down at \(1.5\) ft/s)
57

Since \(r/h=4/8=1/2\), we have \(r=h/2\). Volume: \(V=\frac{1}{3}\pi\!\left(\frac{h}{2}\right)^2 h=\frac{\pi h^3}{12}\). Differentiate: \(\frac{dV}{dt}=\frac{\pi h^2}{4}\frac{dh}{dt}\). With \(\frac{dV}{dt}=-2\) (draining) and \(h=4\): \(-2=\frac{\pi(16)}{4}\frac{dh}{dt}\Rightarrow\frac{dh}{dt}=-\frac{2}{4\pi}=-\frac{1}{2\pi}\,\text{m/min}\).

\(\dfrac{dh}{dt}=-\dfrac{1}{2\pi}\approx-0.159\,\text{m/min}\)
58

Let \(z\) be distance between cars. \(z^2=x^2+y^2\) where \(x=80t,y=60t\). After 1 hour: \(x=80,y=60,z=100\). \(2z\frac{dz}{dt}=2x\frac{dx}{dt}+2y\frac{dy}{dt}\Rightarrow\frac{dz}{dt}=\frac{80(80)+60(60)}{100}=\frac{6400+3600}{100}=100\,\text{mph}\).

\(\dfrac{dz}{dt}=100\,\text{mph}\)
59

\(f\) is continuous on \([0,2]\) (polynomial) and differentiable on \((0,2)\) — MVT applies. Average rate: \(\frac{f(2)-f(0)}{2-0}=\frac{(8-2)-0}{2}=3\). Set \(f'(c)=3x^2-1=3\Rightarrow x^2=\frac{4}{3}\Rightarrow c=\frac{2}{\sqrt{3}}=\frac{2\sqrt{3}}{3}\approx1.155\in(0,2)\). ✓

\(c=\dfrac{2\sqrt{3}}{3}\approx1.155\)
60

\(P'(x)=-0.04x+120\). At \(x=2000\): \(P'(2000)=-0.04(2000)+120=-80+120=40\) dollars/unit. Since \(P'(2000)>0\), profit is still increasing — production should be increased. At \(x=3000\), \(P'=0\) (maximum profit).

Marginal profit at \(x=2000\) is \(\$40/\text{unit}\). Increase production (profit still rising).

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