Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 8 - Techniques of Integration - Chapter Review Exercises - Page 460: 6

Answer

$$3 \ln |x-5|+\ln |x+3|+C$$

Work Step by Step

Given $$\int \frac{4 x+4}{(x-5)(x+3)} d x$$ Since \begin{aligned} \frac{4 x+4}{(x-5)(x+3)} &=\frac{A}{(x-5)}+\frac{B}{(x+3)} \\ &= \frac{A(x+3)+B(x-5)}{(x-5)(x+3)} \\ 4 x+4 &=A(x+3)+B(x-5) \end{aligned} Then \begin{align*} \text{at }\ x&= 5\ \ \ \ \ \ \ \ A= 3\\ \text{at }\ x&= -3\ \ \ \ \ \ \ \ B= 1 \end{align*} Hence \begin{aligned} \int \frac{4 x+4}{(x-5)(x+3)} d x &=\int \frac{3}{(x-5)} d x+\int \frac{1}{(x+3)} d x \\ &=3 \ln |x-5|+\ln |x+3|+C \end{aligned}
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