Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 7 - Techniques of Integration - 7.5 Strategy for Integration - 7.5 Exercises - Page 547: 12

Answer

$$-\ln x+\frac{1}{2}\ln |x^2+3| +\frac{2}{\sqrt{3}} \tan^{-1}\frac{x}{\sqrt{3}}+c$$

Work Step by Step

Given $$\int\frac{2x-3}{x^3+3x}dx$$ Since \begin{align*} \frac{2x-3}{x^3+3x}&=\frac{A}{x }+\frac{Bx+C}{x^2+3 }\\ &=\frac{Bx^2+Cx+Ax^2+3A}{x^2+3 }\\ 2x-3&= Bx^2+Cx+Ax^2+3A \end{align*} At $x=0\to A=-1$ and $ A+B=0\to B=1$ , $C=2$ , then \begin{align*} \int\frac{2x-3}{x^3+3x}dx&=\int\frac{-1}{x }dx+\int\frac{ x+2}{x^2+3 }dx\\ &=\int\frac{-1}{x }dx+\int\frac{ x }{x^2+3 }dx+\int\frac{ 2}{x^2+3 }dx\\ &=-\ln x+\frac{1}{2}\ln |x^2+3| +\frac{2}{\sqrt{3}} \tan^{-1}\frac{x}{\sqrt{3}}+c \end{align*}
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