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 548: 55

Answer

$$2\ln |\sqrt{x}| -2\ln |1+\sqrt{x}|+C$$

Work Step by Step

Given $$\int \frac{d x}{x+x \sqrt{x}}$$ Let $$u^2 =x \ \ \to \ \ 2udu=dx $$ Then \begin{aligned} \int \frac{d x}{x+x \sqrt{x}}&=\int \frac{2ud u}{u^2+u^2 \sqrt{u^2}}\\ &=\int \frac{2ud u}{u^2+u^3 }\\ &=\int \frac{2du }{u^2+u } \end{aligned} Use partial fraction , since \begin{aligned} \frac{2}{u\left(u+1\right)}&=\frac{a_0}{u}+\frac{a_1}{u+1}\\ &=\frac{a_0\left(u+1\right)+a_1u}{u\left(u+1\right)}\\ 2&=a_0\left(u+1\right)+a_1u \end{aligned} at $u=0\to a_0=2,\ \ \ u= -1\to a_1 = -2$, then \begin{aligned} \int \frac{d x}{x+x \sqrt{x}} &=\int \frac{2du }{u^2+u } \\ &=\int \frac{2}{u}du-\int\frac{2}{u+1}du\\ &=2\ln |u| -2\ln |1+u|+C\\ &=2\ln |\sqrt{x}| -2\ln |1+\sqrt{x}|+C \end{aligned}
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