Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 7 - Section 7.4 - Integration of Rational Functions by Partial Fractions. - 7.4 Exercises - Page 501: 23

Answer

$\displaystyle \ln|x-1|-\frac{1}{2}\ln(x^{2}+9)-\frac{1}{3} \arctan(\frac{x}{3})+C$

Work Step by Step

$ I=\displaystyle \int\frac{10}{(x-1)(x^{2}+9)}dx$ $\displaystyle \frac{10}{(x-1)(x^{2}+9)}=\frac{A}{x-1}+\frac{Bx+C}{x^{2}+9}$ $10=A(x^{2}+9)+(Bx+C)(x-1)$ $10=Ax^{2}+9A+Bx^{2}-Bx+Cx-C$ $10=x^{2}(A+B)+x(-B+C)+(9A-C)$ $\left\{\begin{array}{lllll} A & +B & & =0 & \Rightarrow A=-B\\ & -B & +C & =0 & \Rightarrow C=B=-A\\ 9A & & -C & =10 & \end{array}\right.$ Eq 3$\Rightarrow$9A+A=10 $\Rightarrow A=1,B=C=-1$ $\displaystyle \frac{10}{(x-1)(x^{2}+9)}=\frac{1}{x-1}+\frac{-x-1}{x^{2}+9}=\frac{1}{x-1}-\frac{x+1}{x^{2}+9}$ $=\displaystyle \frac{1}{x-1}-\frac{1}{2}\cdot\frac{2x}{x^{2}+9}-\frac{1}{x^{2}+3^2}$ $I=\displaystyle \ln|x-1|-\frac{1}{2}\ln(x^{2}+9)-\frac{1}{3} \arctan(\frac{x}{3})+C$
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