University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 8 - Section 8.4 - Integration of Rational Functions by Partial Fractions - Exercises - Page 446: 45

Answer

$$\int\frac{1}{x^{3/2}-\sqrt x}dx=\ln|\sqrt x-1|-\ln|\sqrt x+1|+C$$

Work Step by Step

$$I=\int\frac{1}{x^{3/2}-\sqrt x}dx=\int\frac{1}{\sqrt x(x-1)}dx$$ We set $u=\sqrt x$, so $$du=\frac{1}{2\sqrt x}dx$$ $$\frac{1}{\sqrt x}dx=2du$$ Also, $x-1=u^2-1$ $$I=\int\frac{2}{u^2-1}du=\int\frac{2}{(u-1)(u+1)}du$$ $$I=\int\frac{(u+1)-(u-1)}{(u-1)(u+1)}du$$ $$I=\Big(\int\frac{du}{u-1}-\int\frac{du}{u+1}\Big)$$ $$I=\ln|u-1|-\ln|u+1|+C$$ $$I=\ln|\sqrt x-1|-\ln|\sqrt x+1|+C$$
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