Aimathic
Login | English | Deutsch

Calculus math worksheets

Build your own math worksheets from 35,000+ problems for grades 3 to 12, from fractions to AP Calculus. Every problem comes with step-by-step solutions.

Partial fractions

Learning goals

  • Factors the denominator and identifies the appropriate decomposition form.
  • Determines unknown coefficients.
  • Integrates the decomposed rational expression.
  • Checks algebraic equivalence before or after integration.

Click problems to add them to your worksheet.

Partial fractions 1
Before finding any coefficients, write the standard partial-fraction decomposition form for \(\frac{5x+1}{(x-2)(x+3)}\).

Hints

- Factor type determines the shape of each term in a partial-fraction decomposition. - Each distinct linear factor needs its own constant numerator.

Solution

1. The denominator has two distinct linear factors, \(x-2\) and \(x+3\). 2. A distinct linear factor contributes one constant numerator over that factor. 3. Therefore the standard form is \(\frac{A}{x-2}+\frac{B}{x+3}\).

Answer

\(\frac{A}{x-2}+\frac{B}{x+3}\)
Partial fractions 2
Write the correct partial-fraction form for \(\frac{1}{x(x-2)^2}\). Use unknown coefficients \(A\), \(B\), and \(C\); do not solve for them.

Hints

- Factor the denominator and check whether any factor repeats. - If you keep only one fraction for a repeated factor, could its numerator reproduce every possible term after combining denominators?

Solution

1. The factor \(x\) appears once, so include \(\frac{A}{x}\). 2. The factor \(x-2\) appears twice, so include both \(\frac{B}{x-2}\) and \(\frac{C}{(x-2)^2}\).

Answer

\(\frac{A}{x}+\frac{B}{x-2}+\frac{C}{(x-2)^2}\)
Partial fractions 3
Set up a partial-fraction decomposition for \(\frac{2x+1}{(x-1)(x^2+4)}\). Use unknown coefficients, but do not find them.

Hints

- Identify the linear factor and the quadratic that has no real roots. - Think about the degree of the numerator you can place over each kind of denominator while keeping the fraction proper. - Check whether your proposed terms could produce both the constant and the \(x\)-term in the original numerator.

Solution

1. The linear factor \(x-1\) contributes a constant numerator: \(\frac{A}{x-1}\). 2. The irreducible quadratic factor \(x^2+4\) needs a general linear numerator: \(\frac{Bx+C}{x^2+4}\).

Answer

\(\frac{A}{x-1}+\frac{Bx+C}{x^2+4}\)
Partial fractions 4
In the decomposition \(\frac{5}{(x-1)(x+4)}=\frac{A}{x-1}+\frac{B}{x+4}\), find \(A\) by substituting a convenient x-value after clearing denominators.

Hints

- Multiply by the common denominator first. - Choose the x-value that makes the term involving \(B\) vanish.

Solution

1. Multiply by \((x-1)(x+4)\) to get \(5=A(x+4)+B(x-1)\). 2. Set \(x=1\): \(5=5A\), so \(A=1\).

Answer

\(A=1\)
Partial fractions 5
To decompose \(\frac{x^2+1}{x(x-1)}\) into partial fractions, a polynomial term is needed first. What is that polynomial term, and why?

Hints

- Compare the degrees of numerator and denominator. - Divide the leading term of the numerator by the leading term of the denominator. - A proper remainder is required before setting up simple partial fractions.

Solution

1. The numerator and denominator both have degree \(2\), with leading coefficient \(1\). 2. Polynomial division gives a quotient of \(1\): \(\frac{x^2+1}{x(x-1)}=1+\frac{x+1}{x(x-1)}\). 3. Only the remaining proper fraction is split into partial fractions.

Answer

The polynomial term is \(1\), because the leading terms of numerator and denominator are both \(x^2\).
Partial fractions 6
An antiderivative of a rational function is \(F(x)=3\ln|x-2|-2\ln|x+1|\). Find \(F'(x)\) as one rational expression. Then state the corresponding indefinite integral.

Hints

- Differentiate each logarithmic term separately. - Combine the resulting simple fractions using one common denominator. - Check the numerator after distributing both coefficients.

Solution

1. Differentiate the logarithms: \(F'(x)=\frac{3}{x-2}-\frac{2}{x+1}\). 2. Use the common denominator \((x-2)(x+1)\). 3. The numerator is \(3(x+1)-2(x-2)=x+7\). 4. Therefore \(F'(x)=\frac{x+7}{(x-2)(x+1)}\), and its indefinite integral is \(3\ln|x-2|-2\ln|x+1|+C\).

Answer

\(F'(x)=\frac{x+7}{(x-2)(x+1)}\) \(\int\frac{x+7}{(x-2)(x+1)}\,\text{d}x=3\ln|x-2|-2\ln|x+1|+C\)
Partial fractions 7
Factor the denominator, decompose, and evaluate: \(\int\frac{3x+2}{x^2-x-6}\,\text{d}x\).

Hints

- The denominator must be written as distinct linear factors first. - Use each root to isolate one numerator constant. - Recombine the fractions before integrating if a coefficient sign seems uncertain.

Solution

1. Factor \(x^2-x-6=(x-3)(x+2)\). 2. Write \(\frac{3x+2}{(x-3)(x+2)}=\frac{A}{x-3}+\frac{B}{x+2}\). 3. Substituting the roots gives \(A=\frac{11}{5}\) and \(B=\frac{4}{5}\). 4. The antiderivative is \(\frac{11}{5}\ln|x-3|+\frac{4}{5}\ln|x+2|+C\).

Answer

\(\frac{11}{5}\ln|x-3|+\frac{4}{5}\ln|x+2|+C\)
Partial fractions 8
Evaluate \(\int\frac{3x+5}{(x-1)^2}\,\text{d}x\) by decomposing the integrand into terms over \(x-1\) and \((x-1)^2\).

Hints

- A repeated linear factor requires one term for each power of that factor. - Recombine the two proposed terms and match the numerator coefficients. - Integrate the first term logarithmically and the second as a negative power.

Solution

1. Use the repeated-factor form \(\frac{3x+5}{(x-1)^2}=\frac{A}{x-1}+\frac{B}{(x-1)^2}\). 2. Recombining gives \(3x+5=A(x-1)+B\), so \(A=3\) and \(B=8\). 3. Integrate term by term: \(\int\left[\frac{3}{x-1}+\frac{8}{(x-1)^2}\right]\,\text{d}x=3\ln|x-1|-\frac{8}{x-1}+C\).

Answer

\(\frac{3x+5}{(x-1)^2}=\frac{3}{x-1}+\frac{8}{(x-1)^2}\) \(\int\frac{3x+5}{(x-1)^2}\,\text{d}x=3\ln|x-1|-\frac{8}{x-1}+C\)
Partial fractions 9
For the proper rational function \(\frac{x^2+1}{(x-3)^2(x^2+9)}\), write the standard real partial-fraction decomposition form. Do not solve for the coefficients.

Hints

- Include a term for every power of a repeated linear factor. - Use a numerator of degree one less than an irreducible quadratic factor. - This problem asks only for the decomposition structure, not the coefficient values.

Solution

1. The repeated linear factor \((x-3)^2\) requires one constant-numerator term for \(x-3\) and one for \((x-3)^2\). 2. The irreducible quadratic factor \(x^2+9\) requires a linear numerator. 3. Therefore, the standard form is \(\frac{A}{x-3}+\frac{B}{(x-3)^2}+\frac{Cx+D}{x^2+9}\).

Answer

\(\frac{A}{x-3}+\frac{B}{(x-3)^2}+\frac{Cx+D}{x^2+9}\)
Partial fractions 10
Evaluate exactly: \(\int_0^1\frac{x+4}{x^2+5x+6}\,\text{d}x\).

Hints

- Factor the quadratic into the two consecutive linear factors. - The numerator can be reconstructed from two constant partial-fraction coefficients. - Combine the endpoint ratios after applying their coefficients.

Solution

1. Factor \(x^2+5x+6=(x+2)(x+3)\). 2. Partial fractions give \(\frac{x+4}{(x+2)(x+3)}=\frac{2}{x+2}-\frac{1}{x+3}\). 3. Endpoint evaluation gives \(2\ln\left(\frac{3}{2}\right)-\ln\left(\frac{4}{3}\right)\). 4. Combining logarithms yields \(\ln\left(\frac{27}{16}\right)\).

Answer

\(\ln\left(\frac{27}{16}\right)\)
Partial fractions 11
Evaluate by partial fractions: \(\int\frac{3x+7}{(x+1)(x+2)}\,dx\). First write the decomposition form, then determine its coefficients.

Hints

- Use one constant numerator for each distinct linear factor. - Multiply by the common denominator before solving for the coefficients. - Substituting the zeros of the denominator factors isolates one coefficient at a time.

Solution

1. Write \(\frac{3x+7}{(x+1)(x+2)}=\frac{A}{x+1}+\frac{B}{x+2}\). 2. Combining the fractions gives \(3x+7=A(x+2)+B(x+1)\). 3. Substitute \(x=-1\) to obtain \(A=4\), and substitute \(x=-2\) to obtain \(B=-1\). 4. Therefore, \(\int\frac{3x+7}{(x+1)(x+2)}\,dx=4\ln|x+1|-\ln|x+2|+C\).

Answer

\(4\ln|x+1|-\ln|x+2|+C\)
Partial fractions 12
The graph of a rational function \(r\) has two vertical asymptotes. Which partial-fraction form fits its behavior near both asymptotes? A. \(\frac{A}{x+1}+\frac{B}{x-2}\) B. \(\frac{A}{(x+1)^2}+\frac{B}{(x-2)^2}\) Explain using the signs of the graph on either side of each asymptote.
Figure for problem 562603

Hints

- Look separately at the branches just left and right of each dashed line. - Decide whether the graph has the same sign or opposite signs on the two sides. - Try a positive and a negative number in each proposed denominator factor. Compare what happens near zero.

Solution

1. At both vertical asymptotes, the graph tends to opposite infinities when approached from opposite sides. 2. A simple linear denominator changes sign when its factor passes through zero; a squared denominator does not. 3. Choice A is consistent with the simple-pole behavior of the plotted graph.

Answer

A. The graph changes sign across each asymptote, matching simple linear factors rather than squared factors.
Partial fractions 13
A rational function has been written as \(\frac{2}{x-1}-\frac{3}{x+2}\). a) Combine the terms to check the original single fraction. b) Use the separated terms to write an antiderivative on any interval that excludes \(-2\) and \(1\).

Hints

- Use the two linear factors as a common denominator to recombine the fractions. - Expand the numerator only after writing both contributions. - The separated terms are easier to integrate than the combined rational expression.

Solution

1. Put the terms over a common denominator: \(\frac{2(x+2)-3(x-1)}{(x-1)(x+2)}=\frac{7-x}{(x-1)(x+2)}\). 2. Integrate each separated term: \(2\ln|x-1|-3\ln|x+2|+C\).

Answer

a) \(\frac{7-x}{(x-1)(x+2)}\) b) \(2\ln|x-1|-3\ln|x+2|+C\)
Partial fractions 14
Valentina claims \(\frac{1}{(x-1)(x+2)}=\frac{1}{3(x-1)}+\frac{1}{3(x+2)}\). Identify the error, write the correct decomposition, and evaluate \(\int\frac{1}{(x-1)(x+2)}\,\text{d}x\).

Hints

- Recombine the proposed fractions before deciding whether they are correct. - Values that make the denominator factors zero can isolate the unknown constants. - A sign difference in the decomposition should also appear between the logarithmic terms.

Solution

1. Recombining Valentina's fractions gives \(\frac{2x+1}{3(x-1)(x+2)}\), not the original numerator \(1\). 2. Let \(\frac{1}{(x-1)(x+2)}=\frac{A}{x-1}+\frac{B}{x+2}\). 3. Substitution at the roots gives \(A=\frac13\) and \(B=-\frac13\). 4. The integral is \(\frac13\ln|x-1|-\frac13\ln|x+2|+C\).

Answer

The second sign should be negative: \(\frac{1}{(x-1)(x+2)}=\frac{1}{3(x-1)}-\frac{1}{3(x+2)}\). The integral is \(\frac13\ln|x-1|-\frac13\ln|x+2|+C\).
Partial fractions 15
Decompose into partial fractions and evaluate: \(\int\frac{2x^2+3x-2}{(x-1)(x+1)(x+2)}\,\text{d}x\).

Hints

- Include a term for every distinct linear factor, even if one coefficient may later be zero. - Use the three roots to isolate the constants efficiently. - A zero coefficient should be retained as a conclusion, not assumed at the start.

Solution

1. Write the decomposition with constants over \(x-1\), \(x+1\), and \(x+2\). 2. Substituting \(x=1\), \(x=-1\), and \(x=-2\) gives \(A=\frac{1}{2}\), \(B=\frac{3}{2}\), and \(C=0\). 3. Thus the integrand is \(\frac{1}{2(x-1)}+\frac{3}{2(x+1)}\). 4. The antiderivative is \(\frac{1}{2}\ln|x-1|+\frac{3}{2}\ln|x+1|+C\).

Answer

\(\frac{2x^2+3x-2}{(x-1)(x+1)(x+2)}=\frac{1}{2(x-1)}+\frac{3}{2(x+1)}\) \(\frac{1}{2}\ln|x-1|+\frac{3}{2}\ln|x+1|+C\)
Partial fractions 16
On the interval \((-1,3)\), find the antiderivative \(F\) of \(f(x)=\frac{4x-1}{(x-3)(x+1)}\) that satisfies \(F(0)=2\).

Hints

- Decompose the rational function into terms with one linear denominator each. - Use the stated interval to write logarithms with positive arguments. - Apply the point condition only after finding the full antiderivative family.

Solution

1. Partial fractions give \(f(x)=\frac{11}{4(x-3)}+\frac{5}{4(x+1)}\). 2. On \((-1,3)\), one antiderivative family is \(F(x)=\frac{11}{4}\ln(3-x)+\frac{5}{4}\ln(x+1)+C\). 3. The condition \(F(0)=2\) gives \(2=\frac{11}{4}\ln3+C\), so \(C=2-\frac{11}{4}\ln3\). 4. Therefore, \(F(x)=2+\frac{11}{4}\ln\left(\frac{3-x}{3}\right)+\frac{5}{4}\ln(x+1)\).

Answer

\(F(x)=2+\frac{11}{4}\ln\left(\frac{3-x}{3}\right)+\frac{5}{4}\ln(x+1)\), for \(-1<x<3\)
Partial fractions 17
Evaluate \(\int\frac{6x-1}{(2x-1)(x+2)}\,\text{d}x\).

Hints

- Use the zeros of the two linear factors to find the constants. - One denominator has a leading coefficient other than \(1\). - Differentiate each logarithm to confirm its scale factor.

Solution

1. Set \(\frac{6x-1}{(2x-1)(x+2)}=\frac{A}{2x-1}+\frac{B}{x+2}\). 2. Substituting \(x=\frac{1}{2}\) and \(x=-2\) gives \(A=\frac{4}{5}\) and \(B=\frac{13}{5}\). 3. Account for the derivative of \(2x-1\) when integrating its term. 4. The result is \(\frac{2}{5}\ln|2x-1|+\frac{13}{5}\ln|x+2|+C\).

Answer

\(\frac{2}{5}\ln|2x-1|+\frac{13}{5}\ln|x+2|+C\)
Partial fractions 18
A rational function \(R\), written in lowest terms, has numerator \(K(x-1)\), where \(K\ne0\), and denominator \((x+3)(x-2)\). It also satisfies \(R(0)=\frac{2}{3}\). Find \(R(x)\), decompose it into partial fractions, and evaluate \(\int R(x)\,\text{d}x\).

Hints

- Write the rational function in terms of the unknown scale factor \(K\). - Use the given function value to determine \(K\) before decomposing. - Substitute the zeros of the two denominator factors to isolate the partial-fraction coefficients.

Solution

1. The stated numerator and denominator imply \(R(x)=K\frac{x-1}{(x+3)(x-2)}\). 2. Substitute \(x=0\): \(R(0)=K\frac{-1}{(3)(-2)}=\frac{K}{6}\). Since \(R(0)=\frac{2}{3}\), \(K=4\). 3. Partial fractions give \(R(x)=\frac{16}{5(x+3)}+\frac{4}{5(x-2)}\). 4. Therefore, \(\int R(x)\,\text{d}x=\frac{16}{5}\ln|x+3|+\frac{4}{5}\ln|x-2|+C\).

Answer

\(R(x)=\frac{4(x-1)}{(x+3)(x-2)}=\frac{16}{5(x+3)}+\frac{4}{5(x-2)}\) \(\int R(x)\,\text{d}x=\frac{16}{5}\ln|x+3|+\frac{4}{5}\ln|x-2|+C\)
Partial fractions 19
Find the positive number \(b\) such that \(\int_0^b\frac{1}{(x+1)(x+2)}\,\text{d}x=\ln\left(\frac{4}{3}\right)\).

Hints

- First express the rational function as a difference of two simpler fractions. - Keep the variable upper endpoint in the logarithmic expression. - Equal logarithms with positive arguments lead to an algebraic equation.

Solution

1. Decompose \(\frac{1}{(x+1)(x+2)}=\frac{1}{x+1}-\frac{1}{x+2}\). 2. The integral equals \(\ln\left(\frac{b+1}{b+2}\right)-\ln\left(\frac{1}{2}\right)=\ln\left(\frac{2(b+1)}{b+2}\right)\). 3. Equating logarithm arguments gives \(\frac{2(b+1)}{b+2}=\frac{4}{3}\). 4. Solving yields \(b=1\), which is positive.

Answer

\(b=1\)
Partial fractions 20
a) Decompose \(\frac{2x}{x^2-4}\) into partial fractions. b) Use that decomposition to evaluate \(\int_{-1}^{1}\frac{2x}{x^2-4}\,\text{d}x\), and explain why the logarithmic endpoint values cancel.

Hints

- Factor the denominator before introducing unknown partial-fraction coefficients. - Match the coefficients of \(x\) and the constant term in the recombined numerator. - After integrating the decomposition, compare the two logarithmic endpoint values.

Solution

1. Factor \(x^2-4=(x-2)(x+2)\). Write \(\frac{2x}{x^2-4}=\frac{A}{x-2}+\frac{B}{x+2}\). 2. Matching numerators gives \(A+B=2\) and \(2A-2B=0\), so \(A=B=1\). Thus \(\frac{2x}{x^2-4}=\frac{1}{x-2}+\frac{1}{x+2}\). 3. An antiderivative is \(\ln|x-2|+\ln|x+2|\). 4. At \(x=1\) and \(x=-1\), the product \(|x-2||x+2|\) equals \(3\), so the logarithmic endpoint values are equal. The definite integral is \(0\).

Answer

a) \(\frac{2x}{x^2-4}=\frac{1}{x-2}+\frac{1}{x+2}\). b) The antiderivative is \(\ln|x-2|+\ln|x+2|\); its endpoint values are equal, so the integral is \(0\).
Partial fractions 21
A server cache changes at the net rate \(r(t)=\frac{90}{(t+2)(t+5)}\) megabytes per minute for \(0\le t\le3\), where \(t\) is measured in minutes. Find the net change in the cache over the three-minute interval.

Hints

- The requested net change is the integral of the given rate. - Separate the rate into two terms with one linear denominator each. - Retain the units after evaluating the endpoint logarithms.

Solution

1. Decompose \(r(t)=\frac{30}{t+2}-\frac{30}{t+5}\). 2. The net change is \(\int_0^3r(t)\,\text{d}t=30[\ln(t+2)-\ln(t+5)]_0^3\). 3. Endpoint evaluation gives \(30\ln\left(\frac{25}{16}\right)\) megabytes.

Answer

\(30\ln\left(\frac{25}{16}\right)\,\text{MB}\)
Partial fractions 22
Evaluate \(\int\frac{x^3+2x^2-2x+5}{x^2-1}\,\text{d}x\). Your work must include both polynomial division and partial fractions.

Hints

- Reduce the rational function to a polynomial plus a proper fraction first. - Factor the remainder denominator before introducing constants. - Check the answer by differentiating both the polynomial and logarithmic parts.

Solution

1. Polynomial division gives \(\frac{x^3+2x^2-2x+5}{x^2-1}=x+2+\frac{-x+7}{x^2-1}\). 2. Factor the denominator and decompose \(\frac{-x+7}{(x-1)(x+1)}=\frac{3}{x-1}-\frac{4}{x+1}\). 3. Integrating all terms gives \(\frac{x^2}{2}+2x+3\ln|x-1|-4\ln|x+1|+C\).

Answer

\(\frac{x^2}{2}+2x+3\ln|x-1|-4\ln|x+1|+C\)
Partial fractions 23
Find an antiderivative of \(\frac{2x+3}{(x-1)(x+2)}\) and state the intervals on which the formula applies. Explain why integration constants need not match across the excluded points.

Hints

- Decompose the rational function before considering its domain. - The denominator zeros divide the real line into separate intervals. - An arbitrary constant connects antiderivatives only within one connected domain interval.

Solution

1. Partial fractions give \(\frac{2x+3}{(x-1)(x+2)}=\frac{5}{3(x-1)}+\frac{1}{3(x+2)}\). 2. An antiderivative is \(\frac{5}{3}\ln|x-1|+\frac{1}{3}\ln|x+2|+C\). 3. The domain intervals are \((-\infty, -2)\), \((-2, 1)\), and \((1, \infty)\). 4. The rational function is undefined at \(-2\) and \(1\), so an antiderivative on one interval is not connected to an antiderivative on another; each interval may have its own constant.

Answer

\(\frac{5}{3}\ln|x-1|+\frac{1}{3}\ln|x+2|+C\), separately on \((-\infty, -2)\), \((-2, 1)\), and \((1, \infty)\). The constant may differ from interval to interval.
Partial fractions 24
Temuulen writes \(\frac{4x+1}{(x-2)(x+1)}=\frac{1}{x-2}+\frac{3}{x+1}\). Show that the coefficients were assigned to the wrong factors, correct the decomposition, and integrate the rational function.

Hints

- Recombine the proposed fractions to inspect the resulting numerator. - Each root isolates the coefficient attached to the other factor. - The corrected coefficients should reproduce both the variable and constant terms.

Solution

1. The proposed right side recombines to \(\frac{(x+1)+3(x-2)}{(x-2)(x+1)}=\frac{4x-5}{(x-2)(x+1)}\). 2. Substituting \(x=2\) in the correct setup gives the coefficient over \(x-2\) as \(3\). 3. Substituting \(x=-1\) gives the coefficient over \(x+1\) as \(1\). 4. Therefore the integral is \(3\ln|x-2|+\ln|x+1|+C\).

Answer

The correct decomposition is \(\frac{4x+1}{(x-2)(x+1)}=\frac{3}{x-2}+\frac{1}{x+1}\). The integral is \(3\ln|x-2|+\ln|x+1|+C\).
Partial fractions 25
Evaluate exactly: \(\int_0^1\frac{1}{(x+1)(x+2)(x+3)}\,\text{d}x\).

Hints

- Use each of the three roots to obtain one coefficient. - The interval keeps all factor values positive. - Combine half-coefficient logarithms carefully at the end.

Solution

1. Decompose \(\frac{1}{(x+1)(x+2)(x+3)}=\frac{1}{2(x+1)}-\frac{1}{x+2}+\frac{1}{2(x+3)}\). 2. An antiderivative is \(\frac{1}{2}\ln(x+1)-\ln(x+2)+\frac{1}{2}\ln(x+3)\) on \([0, 1]\). 3. Evaluating the endpoints and combining logarithms gives \(\frac{1}{2}\ln\left(\frac{32}{27}\right)\).

Answer

\(\frac{1}{2}\ln\left(\frac{32}{27}\right)\)
Partial fractions 26
For \(\frac{x^2+2}{x(x-2)(x+1)}\), Aoife proposes these decomposition forms: A. \(\frac{A}{x(x-2)}+\frac{B}{x+1}\) B. \(\frac{A}{x}+\frac{B}{x-2}+\frac{C}{x+1}\) C. \(\frac{Ax+B}{x(x-2)(x+1)}\) Choose the standard partial-fraction form, determine its coefficients, and evaluate the integral.

Hints

- Match the decomposition structure to the distinct factors in the denominator. - Once the form is chosen, use each denominator zero separately. - Recombine all three terms to verify the numerator.

Solution

1. Each distinct linear factor requires its own constant numerator, so form B is standard. 2. Substituting \(x=0\), \(x=2\), and \(x=-1\) gives \(A=-1\), \(B=1\), and \(C=1\). 3. Thus the integrand is \(-\frac1x+\frac{1}{x-2}+\frac{1}{x+1}\). 4. The antiderivative is \(-\ln|x|+\ln|x-2|+\ln|x+1|+C\).

Answer

Form B, with \(A=-1\), \(B=1\), and \(C=1\). The integral is \(-\ln|x|+\ln|x-2|+\ln|x+1|+C\).
Partial fractions 27
Use coefficient matching, rather than substituting the denominator zeros, to decompose and integrate \(\frac{4x+7}{(x-1)(x+3)}\).

Hints

- Clear the denominator and expand the numerator identity. - Compare the variable coefficient and constant term separately. - Solve the resulting two-equation system before integrating.

Solution

1. Set \(4x+7=A(x+3)+B(x-1)\). 2. Matching coefficients gives \(A+B=4\) and \(3A-B=7\). 3. Solving gives \(A=\frac{11}{4}\) and \(B=\frac{5}{4}\). 4. The antiderivative is \(\frac{11}{4}\ln|x-1|+\frac{5}{4}\ln|x+3|+C\).

Answer

\(\frac{4x+7}{(x-1)(x+3)}=\frac{11}{4(x-1)}+\frac{5}{4(x+3)}\) \(\frac{11}{4}\ln|x-1|+\frac{5}{4}\ln|x+3|+C\)
Partial fractions 28
Suppose \(\frac{5x+2}{(x-1)(x+4)}=\frac{A}{x-1}+\frac{B}{x+4}\). Clear the denominators and use coefficient matching to obtain one equation for \(A\) and \(B\). Use one denominator root for a second equation, then evaluate the integral.

Hints

- Clear the denominator and compare the coefficient of \(x\) on both sides. - One denominator root isolates one coefficient directly. - Use the coefficient-sum equation to find the remaining value.

Solution

1. Clear the denominators: \(5x+2=A(x+4)+B(x-1)\). 2. Comparing the coefficients of \(x\) gives \(A+B=5\). 3. Substituting \(x=1\) gives \(7=5A\), so \(A=\frac{7}{5}\). 4. Therefore, \(B=5-\frac{7}{5}=\frac{18}{5}\). 5. The antiderivative is \(\frac{7}{5}\ln|x-1|+\frac{18}{5}\ln|x+4|+C\).

Answer

\(A=\frac{7}{5}\), \(B=\frac{18}{5}\) \(\frac{7}{5}\ln|x-1|+\frac{18}{5}\ln|x+4|+C\)
Partial fractions 29
For \(R(x)=\frac{x^2+1}{(x-2)(x+1)(x+3)}\), find each partial-fraction coefficient using a limit such as \(A=\lim_{x\to2}(x-2)R(x)\). Then evaluate \(\int R(x)\,\text{d}x\).

Hints

- Multiply by the factor associated with one denominator zero before taking the matching limit. - Repeat the same coefficient calculation at each denominator zero. - Recombine the three terms if any sign is uncertain.

Solution

1. The coefficient at \(x=2\) is \(A=\frac{2^2+1}{(2+1)(2+3)}=\frac{1}{3}\). 2. The coefficients at \(x=-1\) and \(x=-3\) are \(B=-\frac{1}{3}\) and \(C=1\), respectively. 3. Thus \(R(x)=\frac{1}{3(x-2)}-\frac{1}{3(x+1)}+\frac{1}{x+3}\). 4. The antiderivative is \(\frac{1}{3}\ln|x-2|-\frac{1}{3}\ln|x+1|+\ln|x+3|+C\).

Answer

\(R(x)=\frac{1}{3(x-2)}-\frac{1}{3(x+1)}+\frac{1}{x+3}\) \(\int R(x)\,\text{d}x=\frac{1}{3}\ln|x-2|-\frac{1}{3}\ln|x+1|+\ln|x+3|+C\)
Partial fractions 30
Evaluate \(\int\frac{2x+7}{(x+1)(x^2+4)}\,\text{d}x\) using partial fractions over the real numbers.

Hints

- Use a constant numerator over the linear factor and a linear numerator over the irreducible quadratic. - Match coefficients after recombining the fractions. - Split the quadratic term into a denominator-derivative part and an inverse-tangent part.

Solution

1. Use the form \(\frac{2x+7}{(x+1)(x^2+4)}=\frac{A}{x+1}+\frac{Bx+C}{x^2+4}\). 2. Recombining gives \(2x+7=A(x^2+4)+(Bx+C)(x+1)\). 3. Matching coefficients yields \(A=1\), \(B=-1\), and \(C=3\). 4. Integrate term by term: \(\ln|x+1|-\frac{1}{2}\ln(x^2+4)+\frac{3}{2}\arctan\left(\frac{x}{2}\right)+C\).

Answer

\(\frac{2x+7}{(x+1)(x^2+4)}=\frac{1}{x+1}+\frac{-x+3}{x^2+4}\) \(\ln|x+1|-\frac{1}{2}\ln(x^2+4)+\frac{3}{2}\arctan\left(\frac{x}{2}\right)+C\)
Partial fractions 31
A server transfers data at the rate \(r(t)=\frac{6}{(t+1)(t+3)}\) gigabytes per minute for \(0\le t\le2\), where \(t\) is measured in minutes. How many gigabytes does the server transfer during this interval?

Hints

- Integrate the transfer rate over time to find the total data transferred. - Separate the rational rate into two simpler fractions. - Check that the rate units multiplied by minutes give gigabytes.

Solution

1. Decompose \(r(t)=\frac{3}{t+1}-\frac{3}{t+3}\). 2. The total data transferred is \(\int_0^2r(t)\,\text{d}t=3[\ln(t+1)-\ln(t+3)]_0^2\). 3. Evaluate the endpoints to obtain \(3\ln\left(\frac{9}{5}\right)\,\text{GB}\).

Answer

\(3\ln\left(\frac{9}{5}\right)\,\text{GB}\)
Partial fractions 32
Decompose and evaluate \(\int\frac{-18}{(x-1)(x+2)(x-4)}\,\text{d}x\). Combine the final logarithms into one logarithm.

Hints

- Use each denominator zero to isolate one coefficient. - Integrate the three simple fractions before combining anything. - Positive logarithmic coefficients become numerator powers, while negative ones become denominator powers.

Solution

1. Substituting the three denominator zeros gives coefficients \(2\), \(-1\), and \(-1\). 2. The integrand is \(\frac{2}{x-1}-\frac{1}{x+2}-\frac{1}{x-4}\). 3. The antiderivative is \(2\ln|x-1|-\ln|x+2|-\ln|x-4|+C\). 4. Combining logarithms gives \(\ln\left|\frac{(x-1)^2}{(x+2)(x-4)}\right|+C\).

Answer

\(\ln\left|\frac{(x-1)^2}{(x+2)(x-4)}\right|+C\)
Partial fractions 33
a) Write \(\frac{4x+b}{(x-1)(x+2)}=\frac{A}{x-1}+\frac{B}{x+2}\) and express \(A\) and \(B\) in terms of \(b\). b) Find the real number \(b\) for which the antiderivative can be written as \(c\ln|(x-1)(x+2)|+C\) for some real constant \(c\). Find both \(b\) and \(c\), using your partial-fraction coefficients from part a).

Hints

- Recombine the two partial fractions and match the coefficient of \(x\) and the constant term. - A single logarithm of a product expands into two logarithms with the same coefficient. - Use the coefficient formulas from part a), rather than differentiating the requested final logarithm directly.

Solution

1. Recombining gives \(A(x+2)+B(x-1)=(A+B)x+(2A-B)\). Thus \(A+B=4\) and \(2A-B=b\). 2. Solving gives \(A=\frac{b+4}{3}\) and \(B=\frac{8-b}{3}\). 3. An antiderivative of the decomposition is \(A\ln|x-1|+B\ln|x+2|+C\). 4. For this to equal \(c\ln|(x-1)(x+2)|+C=c\ln|x-1|+c\ln|x+2|+C\), we need \(A=B=c\). 5. Setting \(\frac{b+4}{3}=\frac{8-b}{3}\) gives \(b=2\), and then \(A=B=2\), so \(c=2\).

Answer

a) \(A=\frac{b+4}{3}\) and \(B=\frac{8-b}{3}\). b) \(b=2\) and \(c=2\).
Partial fractions 34
Evaluate \(\int\frac{x+1}{4-x^2}\,\text{d}x\). Factor the denominator in a way that keeps the sign of \(2-x\) visible.

Hints

- Use the difference-of-squares factorization without changing the first factor’s orientation. - Find one constant over each linear factor. - One factor has derivative \(-1\), which affects its logarithmic sign.

Solution

1. Factor \(4-x^2=(2-x)(2+x)\). 2. Decompose \(\frac{x+1}{(2-x)(2+x)}=\frac{3}{4(2-x)}-\frac{1}{4(2+x)}\). 3. Since the derivative of \(2-x\) is \(-1\), its logarithmic term gains another negative sign. 4. The antiderivative is \(-\frac{3}{4}\ln|2-x|-\frac{1}{4}\ln|2+x|+C\).

Answer

\(-\frac{3}{4}\ln|2-x|-\frac{1}{4}\ln|2+x|+C\)
Partial fractions 35
A rational function has denominator \((x+2)(x-1)(x-4)\). Its partial-fraction coefficients are shown. <table><tr><th>Linear factor</th><th>Coefficient</th></tr><tr><td>\(x+2\)</td><td>\(1\)</td></tr><tr><td>\(x-1\)</td><td>\(-2\)</td></tr><tr><td>\(x-4\)</td><td>\(3\)</td></tr></table> Write the function as one rational expression, then give its indefinite integral.

Hints

- Translate each table row directly into one simple fraction. - Use the product of all three factors as the common denominator. - Keep the decomposed form for the integration step.

Solution

1. The decomposed function is \(\frac{1}{x+2}-\frac{2}{x-1}+\frac{3}{x-4}\). 2. Over the common denominator, the numerator is \((x-1)(x-4)-2(x+2)(x-4)+3(x+2)(x-1)=2x^{2}+2x+14\). 3. The rational function is \(\frac{2x^{2}+2x+14}{(x+2)(x-1)(x-4)}\). 4. Its antiderivative is \(\ln|x+2|-2\ln|x-1|+3\ln|x-4|+C\).

Answer

\(\frac{2x^{2}+2x+14}{(x+2)(x-1)(x-4)}\) \(\ln|x+2|-2\ln|x-1|+3\ln|x-4|+C\)
Partial fractions 36
A calibration fluid enters a test chamber at the rate \(r(t)=\frac{k}{(t+1)(t+2)}\) milliliters per minute for \(0\le t\le1\), where \(t\) is measured in minutes and \(k>0\). Find \(k\) if exactly \(10\,\text{mL}\) enters during that minute.

Hints

- The total amount is the integral of the rate over the stated minute. - Decompose the rational factor before carrying the parameter through the integral. - Solve for the positive scale parameter after evaluating the logarithmic change.

Solution

1. Decompose \(\frac{1}{(t+1)(t+2)}=\frac{1}{t+1}-\frac{1}{t+2}\). 2. The accumulated volume is \(k[\ln(t+1)-\ln(t+2)]_0^1=k\ln\left(\frac{4}{3}\right)\). 3. Set this equal to \(10\): \(k\ln\left(\frac{4}{3}\right)=10\). 4. Therefore \(k=\frac{10}{\ln(4/3)}\,\text{mL/min}\).

Answer

\(k=\frac{10}{\ln(4/3)}\,\text{mL/min}\)
Partial fractions 37
Let \(R(x)=\frac{x^2+px-6}{(x-1)(x+2)(x-4)}\). In its partial-fraction decomposition, the coefficient over \(x-4\) is \(-1\). Find \(p\), determine all three coefficients, and evaluate \(\int R(x)\,\text{d}x\).

Hints

- Use the zero of \(x-4\) to express its coefficient directly in terms of \(p\). - After determining \(p\), use the other two denominator zeros to obtain their coefficients. - Integrate each simple fraction logarithmically.

Solution

1. The coefficient over \(x-4\) is found by substituting \(x=4\) after canceling that factor: \(C=\frac{16+4p-6}{(4-1)(4+2)}=\frac{10+4p}{18}\). 2. Set \(C=-1\): \(10+4p=-18\), so \(p=-7\). 3. With \(p=-7\), substitute the other denominator zeros. At \(x=1\), \(A=\frac{1-7-6}{(1+2)(1-4)}=\frac{4}{3}\). At \(x=-2\), \(B=\frac{4+14-6}{(-2-1)(-2-4)}=\frac{2}{3}\). 4. Therefore, \(R(x)=\frac{4}{3(x-1)}+\frac{2}{3(x+2)}-\frac{1}{x-4}\). 5. The antiderivative is \(\frac{4}{3}\ln|x-1|+\frac{2}{3}\ln|x+2|-\ln|x-4|+C\).

Answer

\(p=-7\) \(R(x)=\frac{4}{3(x-1)}+\frac{2}{3(x+2)}-\frac{1}{x-4}\) \(\int R(x)\,\text{d}x=\frac{4}{3}\ln|x-1|+\frac{2}{3}\ln|x+2|-\ln|x-4|+C\)
Partial fractions 38
A drone climbs vertically at \(v(t)=\frac{5t+7}{(t+1)(t+2)}\) meters per second for \(0\le t\le2\), where \(t\) is seconds after takeoff. How much height does it gain during those \(2\) seconds? Use partial fractions.

Hints

- A velocity accumulated over time gives a change in height. - Try a sum of fractions using the two linear denominator factors. - Check the numerators after clearing denominators before integrating.

Solution

1. The height gained is \(\int_0^2\frac{5t+7}{(t+1)(t+2)}\,\text{d}t\). 2. Write \(\frac{5t+7}{(t+1)(t+2)}=\frac{A}{t+1}+\frac{B}{t+2}\). Comparing numerators gives \(A+B=5\) and \(2A+B=7\), so \(A=2\) and \(B=3\). 3. Integrate: \(\left[2\ln(t+1)+3\ln(t+2)\right]_0^2=2\ln(3)+3\ln(2)=\ln(72)\) meters.

Answer

\(\ln(72)\,\text{m}\)
Partial fractions 39
a) Decompose \(\frac{kx+3}{(x+1)(x+2)}\) into partial fractions, with both coefficients written in terms of \(k\). b) Use that decomposition to find the real number \(k\) such that \(\int_0^1\frac{kx+3}{(x+1)(x+2)}\,\text{d}x=\ln3\).

Hints

- Introduce one constant numerator over each distinct linear factor. - Recombine the fractions and match both coefficients with \(kx+3\). - Integrate only after the coefficient formulas are established.

Solution

1. Write \(\frac{kx+3}{(x+1)(x+2)}=\frac{A}{x+1}+\frac{B}{x+2}\). Then \((A+B)x+(2A+B)=kx+3\). 2. Hence \(A+B=k\) and \(2A+B=3\), giving \(A=3-k\) and \(B=2k-3\). 3. Therefore the integral equals \((3-k)\ln2+(2k-3)\ln\left(\frac{3}{2}\right)\). 4. Setting this equal to \(\ln3\) gives \(k=2\). The coefficient of \(k\) in the equation is \(\ln(9/8)\ne0\), so the solution is unique.

Answer

a) \(\frac{kx+3}{(x+1)(x+2)}=\frac{3-k}{x+1}+\frac{2k-3}{x+2}\). b) \(k=2\).
Partial fractions 40
Kärt tries to write \(\frac{2x^2+x+4}{(x-1)(x+2)}=\frac{A}{x-1}+\frac{B}{x+2}\). Explain why this form cannot be correct, then produce a correct decomposition and evaluate the integral.

Hints

- Compare the end behavior of the original expression and the proposed decomposition. - Perform division before decomposing the remainder. - Only the proper fraction should be assigned simple linear denominators.

Solution

1. Kärt's right side approaches \(0\) as \(|x|\) grows, but the original rational function approaches \(2\), so a polynomial term is missing. 2. Division gives \(\frac{2x^2+x+4}{x^2+x-2}=2+\frac{-x+8}{(x-1)(x+2)}\). 3. The proper remainder decomposes as \(\frac{-x+8}{(x-1)(x+2)}=\frac{7}{3(x-1)}-\frac{10}{3(x+2)}\). 4. The integral is \(2x+\frac73\ln|x-1|-\frac{10}{3}\ln|x+2|+C\).

Answer

A constant polynomial term is required: \(\frac{2x^2+x+4}{(x-1)(x+2)}=2+\frac{7}{3(x-1)}-\frac{10}{3(x+2)}\). The integral is \(2x+\frac73\ln|x-1|-\frac{10}{3}\ln|x+2|+C\).
Partial fractions 41
Suppose \(\frac{5x+k}{(x-2)(x+3)}=\frac{A}{x-2}+\frac{B}{x+3}\). Find every real value of \(k\) for which \(AB=6\). For each value, determine \(A\) and \(B\) and evaluate the corresponding indefinite integral.

Hints

- Clear the denominator and compare the leading coefficient first. - Use the given product together with the coefficient sum to find the unordered pair. - The constant term distinguishes the two possible assignments.

Solution

1. Matching the coefficient of \(x\) gives \(A+B=5\). 2. Together with \(AB=6\), the partial-fraction coefficients are the roots of \(z^2-5z+6=0\), so \(\{A, B\}=\{2, 3\}\). 3. The constant term satisfies \(k=3A-2B\). 4. If \((A, B)=(2, 3)\), then \(k=0\), and the integral is \(2\ln|x-2|+3\ln|x+3|+C\). 5. If \((A, B)=(3, 2)\), then \(k=5\), and the integral is \(3\ln|x-2|+2\ln|x+3|+C\).

Answer

\(k=0\): \(A=2\), \(B=3\), and the integral is \(2\ln|x-2|+3\ln|x+3|+C\). \(k=5\): \(A=3\), \(B=2\), and the integral is \(3\ln|x-2|+2\ln|x+3|+C\).

All problems may be used, copied and printed free of charge for school and tutoring, including paid tutoring. Commercial adaptations as well as publication or redistribution on the internet are not permitted.