Calculus: Early Transcendentals 8th Edition

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

Chapter 7 - Section 7.5 - Strategy for Integration - 7.5 Exercises - Page 508: 46

Answer

$\displaystyle \frac{e^{x}}{x}+C$

Work Step by Step

$I=\displaystyle \int\frac{(x-1)e^{x}}{x^{2}}dx=\int(x-1)e^{x}\cdot(\frac{1}{x^{2}})dx=\int udv$ (by parts) $\left[\begin{array}{ll} u=(x-1)e^{x} & dv =\dfrac{1}{x^{2}}dx\\ du=[(x-1)e^{x}+e^{x}]dx \\ du=[xe^{x}-e^{x}+e^{x}]dx & \\ du=xe^{x}dx & v=-\dfrac{1}{x} \end{array}\right]$ $I=uv-\displaystyle \int vdu$ $=(x-1)e^{x}(-\displaystyle \frac{1}{x})-\int xe^{x}(-\frac{1}{x})dx$ This integral is much simpler, so we proceed. $=(x-1)e^{x}(-\displaystyle \frac{1}{x})-\int-e^{x}dx$ $=(-1+\displaystyle \frac{1}{x})e^{x}+\int e^{x}dx$ $=-e^{x}+\displaystyle \frac{e^{x}}{x}+e^{x}+C$ $=\displaystyle \frac{e^{x}}{x}+C$
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