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 - Practice Exercises - Page 519: 70

Answer

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

Work Step by Step

$$\eqalign{ & \int {\frac{{{x^3} + 2}}{{4 - {x^2}}}} dx \cr & \cr & {\text{Use long division }}\frac{{{x^3} + 2}}{{4 - {x^2}}} = - x + \frac{{4x + 2}}{{4 - {x^2}}} \cr & \frac{{{x^3} + 2}}{{4 - {x^2}}} = - x + \frac{{4x}}{{4 - {x^2}}} + \frac{2}{{4 - {x^2}}} \cr & \cr & {\text{Decomposing }}\frac{2}{{4 - {x^2}}}{\text{ into partial fractions}} \cr & \frac{2}{{4 - {x^2}}} = \frac{2}{{\left( {2 + x} \right)\left( {2 - x} \right)}} = \frac{A}{{2 + x}} + \frac{B}{{2 - x}} \cr & 2 = A\left( {2 - x} \right) + B\left( {2 + x} \right) \cr & {\text{If }}x = - 2 \to A = \frac{1}{2} \cr & {\text{If }}x = 2 \to B = \frac{1}{2} \cr & {\text{Then}}{\text{, }}\frac{2}{{4 - {x^2}}} = \frac{{1/2}}{{2 + x}} + \frac{{1/2}}{{2 - x}} \cr & \cr & - x + \frac{{4x}}{{4 - {x^2}}} + \frac{2}{{4 - {x^2}}} = - x + \frac{{4x}}{{4 - {x^2}}} + \frac{1}{{2\left( {2 + x} \right)}} + \frac{1}{{2\left( {2 - x} \right)}} \cr & \cr & \int {\frac{{{x^3} + 2}}{{4 - {x^2}}}} dx = \int {\left( { - x + \frac{{4x}}{{4 - {x^2}}} + \frac{1}{{2\left( {2 + x} \right)}} + \frac{1}{{2\left( {2 - x} \right)}}} \right)} dx \cr & {\text{Integrating}} \cr & = - \frac{{{x^2}}}{2} - 2\ln \left| {4 - {x^2}} \right| + \frac{1}{2}\ln \left| {2 + x} \right| - \frac{1}{2}\ln \left| {2 - x} \right| + C \cr} $$
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.