Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 8: Techniques of Integration - Section 8.2 - Integration by Parts - Exercises 8.2 - Page 455: 35

Answer

$$ - \frac{{\ln x}}{x} - \frac{1}{x} + C $$

Work Step by Step

$$\eqalign{ & \int {\frac{{\ln x}}{{{x^2}}}} dx \cr & {\text{write with negative exponent}} \cr & = \int {{x^{ - 2}}\ln x} dx \cr & {\text{Using integration by parts method }} \cr & \,\,\,\,\,{\text{Let }}u = \ln x,\,\,\,\,du = \frac{1}{x}dx,\,\,\,\,\,dv = {x^{ - 2}}dx,\,\,\,\,v = - {x^{ - 1}} \cr & \cr & {\text{Integration by parts then gives}} \cr & \int {{x^{ - 2}}\ln x} dx = \left( {\ln x} \right)\left( { - {x^{ - 1}}} \right) - \int {\left( { - {x^{ - 1}}} \right)} \left( {\frac{1}{x}dx} \right) \cr & \int {{x^{ - 2}}\ln x} dx = - \frac{{\ln x}}{x} + \int {{x^{ - 2}}} dx \cr & \cr & {\text{Integrate by the power rule}} \cr & \int {{x^{ - 2}}\ln x} dx = - \frac{{\ln x}}{x} + \frac{{{x^{ - 1}}}}{{ - 1}} + C \cr & \int {{x^{ - 2}}\ln x} dx = - \frac{{\ln x}}{x} - \frac{1}{x} + C \cr} $$
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