Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 8 - Techniques of Integration - 8.1 Integration by Parts - Exercises - Page 395: 50

Answer

$$1-\frac{2}{e}$$

Work Step by Step

Given $$\int_{1}^{e} \frac{\ln x d x}{x^{2}}$$ Let \begin{align*} u&=\ln x\ \ \ \ \ \ \ \ dv= x^{-2}dx\\ du&= \frac{ 1}{x} dx\ \ \ \ \ \ \ \ v=-x^{-1} \end{align*} Then \begin{align*} \int_{1}^{e} \frac{\ln x d x}{x^{2}}&= -\frac{1}{x} \ln x\bigg|_{1}^{e} +\int_{1}^{e} \frac{1}{x^2} d x \\ &= -\frac{1}{x} \ln x\bigg|_{1}^{e}-\frac{1}{x}\bigg|_{1}^{e} \\ &=1-\frac{2}{e} \end{align*}
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