A B  C A L C U L U S
Chapter 6

Integration & Accumulation of Change

AP-Style Practice Questions

EASYMEDIUMHARD

Topics 6.1 – 6.10, 6.14AB

+ Extensions: 6.11 IBP · 6.12 Partial Fractions · 6.13 Improper IntegralsBC



Name:Period:
PART ITopics 6.1 – 6.10

Multiple Choice Questions

Show all supporting work on scratch paper. On the AP Exam, Section I is split into a no-calculator and a calculator-allowed part — each question below is labeled accordingly.

Q1EASY6.2 Riemann SumsNo Calculator

The interval $[0,4]$ is divided into four subintervals of equal length. Which expression gives the right Riemann sum approximation for $\displaystyle\int_{0}^{4}f(x)\,dx$?

Q2EASY6.6 PropertiesNo Calculator

If $\displaystyle\int_{0}^{5}f(x)\,dx=12$ and $\displaystyle\int_{0}^{2}f(x)\,dx=3$, then $\displaystyle\int_{2}^{5}f(x)\,dx=$

Q3EASY6.4 FTCNo Calculator

If $F(x)=\displaystyle\int_{1}^{x}t^{2}\,dt$, then $F'(x)=$

Q4MEDIUM6.4 FTC + ChainNo Calculator

If $F(x)=\displaystyle\int_{0}^{x^{2}}\sin t\,dt$, then $F'(x)=$

Q5EASY6.8 AntiderivativesNo Calculator

$\displaystyle\int (3x^{2}-4x+5)\,dx =$

Q6MEDIUM6.9 U-SubstitutionNo Calculator

$\displaystyle\int 2x\,(x^{2}+1)^{4}\,dx =$

Q7MEDIUM6.7 FTC EvaluationNo Calculator

$\displaystyle\int_{0}^{\pi/2}\cos x\,dx =$

Q8MEDIUM6.6 Geometry of IntegralNo Calculator

The graph of $f$ consists of two line segments (forming a triangle above the $x$-axis with vertices $(-2,0)$, $(0,2)$, $(2,0)$) and a semicircle of radius $2$ below the $x$-axis on $[2,6]$. Find $\displaystyle\int_{-2}^{6}f(x)\,dx$.

-2 2 4 6 2 -2
Q9HARD6.9 U-Sub DefiniteNo Calculator

$\displaystyle\int_{0}^{1}\dfrac{x}{(x^{2}+1)^{2}}\,dx =$

Q10MEDIUM6.3 Riemann ↔ IntegralNo Calculator

Which definite integral equals $\displaystyle\lim_{n\to\infty}\sum_{i=1}^{n}\!\left(1+\dfrac{2i}{n}\right)^{2}\!\cdot\dfrac{2}{n}$?

Q11HARD6.2 Over/UnderestimateNo Calculator

$f$ is positive, increasing, and concave down on $[a,b]$. Which of the following must be an underestimate of $\displaystyle\int_{a}^{b}f(x)\,dx$?

Q12MEDIUM6.10 Long DivisionNo Calculator

$\displaystyle\int \dfrac{x^{2}+1}{x+1}\,dx =$

Q13HARD6.2 / 6.4 AccumulationNo Calculator

Selected values of the differentiable function $f$ are given. Let $g(x)=\displaystyle\int_{0}^{x}f(t)\,dt$.

$x$$0$$2$$4$$6$$8$
$f(x)$$5$$3$$-1$$-4$$-2$

Using a midpoint Riemann sum with two subintervals of equal length, the approximation for $g(8)$ is

Q14MEDIUM6.5 Behavior of $g$No Calculator

Let $g(x)=\displaystyle\int_{0}^{x}f(t)\,dt$, where $f$ is continuous and is positive on $(0,3)$, zero at $x=3$, and negative on $(3,5)$. At what value of $x$ does $g$ attain its maximum on $[0,5]$?

Q15EASY6.1 Accumulation UnitsNo Calculator

Water flows into a tank at a rate $r(t)$ gallons per minute, where $t$ is in minutes. The most appropriate units of $\displaystyle\int_{0}^{10}r(t)\,dt$ are

Q16HARD6.10 Completing the SquareNo Calculator

$\displaystyle\int \dfrac{1}{x^{2}+2x+5}\,dx =$

Q17MEDIUM6.14 Selecting a TechniqueNo Calculator

Which technique is most appropriate for evaluating $\displaystyle\int x\sec^{2}(x^{2})\,dx$?

Q18MEDIUM6.6 PropertiesNo Calculator

If $\displaystyle\int_{1}^{4}\bigl[\,2f(x)-3\,\bigr]\,dx = 14$ and $\displaystyle\int_{1}^{4}f(x)\,dx = ?$

PART IIShow All Work

Free-Response Questions

Free-response answers must include all setup. When using a calculator, present the integral expression with limits and a differential before evaluating. When without a calculator, show antiderivatives, the constant of integration on indefinite integrals, and careful use of substitution.

FRQ 1EASY6.7 / 6.8 / 6.9 EvaluationNo Calculator

Evaluate each of the following. Show all work.

(a) $\displaystyle\int_{1}^{2}(4x^{3}-6x+1)\,dx$
(b) $\displaystyle\int \cos(3x)\,dx$
(c) $\displaystyle\int x\,e^{x^{2}}\,dx$
FRQ 2MEDIUM6.1 / 6.2 / 6.3 ReservoirCalculator

The rate at which water enters a reservoir is modeled by the differentiable function $R(t)$, where $R$ is in thousands of gallons per hour and $t$ is in hours since midnight. Selected values of $R$:

$t$ (hr)$0$$3$$6$$9$$12$
$R(t)$$5.2$$6.8$$8.1$$7.4$$4.5$
(a) Use a left Riemann sum with the four subintervals shown to approximate $\displaystyle\int_{0}^{12}R(t)\,dt$. Using correct units, explain the meaning of this integral in context.
(b) Use a trapezoidal sum with the four subintervals shown to approximate $\displaystyle\int_{0}^{12}R(t)\,dt$.
(c) Is the left Riemann sum in part (a) an over- or under-estimate? Explain using the behavior of $R$ shown in the table, or state what additional information would be needed to decide.
(d) The reservoir holds $W(t)$ thousand gallons at time $t$. Water leaves the reservoir at a constant rate of $4$ thousand gallons per hour during the $12$-hour period. Write, but do not evaluate, an expression involving an integral for $W(12)$ given $W(0)=80$.
FRQ 3MEDIUM6.4 / 6.5 Accumulation FunctionNo Calculator

The graph of the continuous function $f$ on $[0,8]$ consists of three line segments and a quarter circle of radius $2$, as shown. Let $g(x)=\displaystyle\int_{0}^{x}f(t)\,dt$.

2 4 6 8 2 -2
(a) Find $g(2)$, $g(4)$, and $g(8)$.
(b) On what interval(s) is $g$ increasing? Justify.
(c) At what value of $x$ on $[0,8]$ does $g$ attain its absolute maximum? Justify.
(d) Find the $x$-coordinate of each point of inflection of $g$ on $(0,8)$. Justify.
FRQ 4HARD6.8 / 6.9 / 6.10 TechniquesNo Calculator

Evaluate each of the following integrals, showing all algebraic steps. For $u$-substitution problems, clearly state your choice of $u$ and $du$.

(a) $\displaystyle\int \dfrac{2x+3}{x^{2}+3x+5}\,dx$
(b) $\displaystyle\int_{0}^{1}x\sqrt{1-x^{2}}\,dx$
(c) $\displaystyle\int \dfrac{x^{2}+1}{x-2}\,dx$
FRQ 5HARD6.4 / 6.5 / 6.7 Reasoning with $g$No Calculator

Let $f$ be a continuous function on $[-2,8]$, and define $g(x)=\displaystyle\int_{0}^{x}f(t)\,dt$. It is known that $\displaystyle\int_{0}^{3}f(t)\,dt=6$, $\displaystyle\int_{3}^{5}f(t)\,dt=-2$, and $\displaystyle\int_{5}^{8}f(t)\,dt=4$.

(a) Find $g(3)$, $g(5)$, and $g(8)$.
(b) Find $\displaystyle\int_{-1}^{8}\bigl[\,2f(t)+1\,\bigr]\,dt$, given that $\displaystyle\int_{-1}^{0}f(t)\,dt = 1$.
(c) Suppose $f$ is differentiable on $[0,8]$, with $f(0)=2$ and $f(8)=-3$. Let $h(x)=x\cdot f(x)$. Find $\displaystyle\int_{0}^{8}\bigl[\,f(x)+x\,f'(x)\,\bigr]\,dx$.
(d) Let $H(x)=\displaystyle\int_{0}^{x^{2}}f(t)\,dt$. Express $H'(x)$ in terms of $f$ and $x$.
PART III — (BC) EXTENSIONSTopics 6.11, 6.12, 6.13 — BC ONLY

BC-Only Practice

BC ONLY. The following items cover Integration by Parts (Topic 6.11), Linear Partial Fractions (Topic 6.12), and Improper Integrals (Topic 6.13). AB students may skip this section. BC students should be fluent with: (i) IBP $\displaystyle\int u\,dv = uv-\int v\,du$ — pick $u$ via LIATE; (ii) decomposing proper rationals with distinct linear factors as $\dfrac{A}{x-r_1}+\dfrac{B}{x-r_2}+\cdots$; (iii) evaluating improper integrals as limits, including those with interior discontinuities (split first).
Q BC1MEDIUM6.11 IBPBC ONLYNo Calculator

$\displaystyle\int_{0}^{1}x\,e^{x}\,dx=$

Q BC2MEDIUM6.12 Partial FractionsBC ONLYNo Calculator

The partial-fraction decomposition of $\dfrac{1}{x^{2}-1}$ is

Q BC3EASY6.13 ImproperBC ONLYNo Calculator

$\displaystyle\int_{1}^{\infty}\dfrac{1}{x^{2}}\,dx=$

Q BC4MEDIUM6.13 Improper (Compare)BC ONLYNo Calculator

Which of the following improper integrals diverge?

FRQ BC1HARD6.11 IBP (Twice)BC ONLYNo Calculator

Evaluate each integral using integration by parts. State your choice of $u$ and $dv$ at every step.

(a) $\displaystyle\int x^{2}\,e^{x}\,dx$ — apply IBP twice.
(b) $\displaystyle\int_{1}^{e}\ln x\,dx$ — use $u=\ln x$, $dv=dx$.
(c) Briefly explain how the LIATE mnemonic guided your $u$ selection in parts (a) and (b).
FRQ BC2HARD6.12 / 6.13 Partial Fractions + ImproperBC ONLYNo Calculator

Consider $\displaystyle\int_{2}^{\infty}\dfrac{1}{x^{2}-x}\,dx$.

(a) Decompose $\dfrac{1}{x^{2}-x}$ into partial fractions. Show the algebraic system you solve.
(b) Set up the integral as a limit, evaluate the antiderivative, and determine whether the integral converges. If it converges, give the exact value.
(c) Now consider $\displaystyle\int_{0}^{2}\dfrac{1}{(x-1)^{1/3}}\,dx$, which is improper at the interior point $x=1$. Split the integral, evaluate each piece as a one-sided limit, and find the total value (or state divergence). Justify each step.