Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 8: Techniques of Integration - Section 8.5 - Integration of Rational Functions by Partial Fractions - Exercises 8.5 - Page 475: 20

Answer

$$\frac{1}{4}\ln \left| {x - 1} \right| + \frac{3}{4}\ln \left| {x + 1} \right| + \frac{1}{{2\left( {x + 1} \right)}} + C$$

Work Step by Step

$$\eqalign{ & \int {\frac{{{x^2}dx}}{{\left( {x - 1} \right)\left( {{x^2} + 2x + 1} \right)}}} \cr & {\text{Decompose the integrand }}\frac{{{x^2}}}{{\left( {x - 1} \right)\left( {{x^2} + 2x + 1} \right)}}{\text{ into partial fractions}} \cr & \frac{{{x^2}}}{{\left( {x - 1} \right)\left( {{x^2} + 2x + 1} \right)}} = \frac{{{x^2}}}{{\left( {x - 1} \right){{\left( {x + 1} \right)}^2}}} = \frac{A}{{x - 1}} + \frac{B}{{x + 1}} + \frac{C}{{{{\left( {x + 1} \right)}^2}}} \cr & {\text{Multiply by }}\left( {x - 1} \right){\left( {x + 1} \right)^2}{\text{ and simplify}} \cr & {x^2} = A{\left( {x + 1} \right)^2} + B\left( {x + 1} \right)\left( {x - 1} \right) + C\left( {x - 1} \right) \cr & {x^2} = A{x^2} + 2Ax + A + B{x^2} - B + Cx - C \cr & {\text{Group terms}} \cr & {x^2} = \left( {A{x^2} + B{x^2}} \right) + \left( {2Ax + Cx} \right) + A - B - C \cr & {\text{Equating coefficients, we get}} \cr & A + B = 1,\,\,\,2A + C = 0,\,\,\,A - B - C = 0 \cr & {\text{Solving the system of linear equation by a calculator, we obtain}} \cr & A = \frac{1}{4},\,\,\,B = \frac{3}{4},\,\,C = - \frac{1}{2},\,\, \cr & {\text{Therefore}}{\text{,}} \cr & \frac{{{x^2}}}{{\left( {x - 1} \right)\left( {{x^2} + 2x + 1} \right)}} = \frac{{1/4}}{{x - 1}} + \frac{{3/4}}{{x + 1}} + \frac{{ - 1/2}}{{{{\left( {x + 1} \right)}^2}}} \cr & \int {\frac{{{x^2}dx}}{{\left( {x - 1} \right)\left( {{x^2} + 2x + 1} \right)}}} = \int {\left( {\frac{{1/4}}{{x - 1}} + \frac{{3/4}}{{x + 1}} + \frac{{ - 1/2}}{{{{\left( {x + 1} \right)}^2}}}} \right)} dx \cr & {\text{Integrating, we get}} \cr & = \frac{1}{4}\ln \left| {x - 1} \right| + \frac{3}{4}\ln \left| {x + 1} \right| + \frac{1}{{2\left( {x + 1} \right)}} + C \cr} $$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.