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: 33

Answer

$\frac{x^{2}}{2}(\ln x)^{2}-\frac{x^{2} \ln x}{2}+\frac{x^{2}}{4}+C $

Work Step by Step

$$ \begin{aligned} & \int x(\ln x)^{2} d x\\ & \text { } \\ & \text { "Integrate by parts" } \\ & u=(\ln x)^{2} \quad d v=x d x \\ & d u=2 \ln x \cdot \frac{1}{x} d x \quad v=\frac{x^{2}}{2} \\ & u \cdot v-\int v d u \\ & \text { } \\ & (\ln x)^{2} \frac{x^{2}}{2}-\int \frac{x^{2}}{2} \frac{2 \ln x}{x} d x \\ & (\ln x)^{2} \frac{x^{2}}{2}-\int x \ln x d x \\ & \text { } \\ & \text { "Integrate by parts again" } \\ & \quad u=\ln x \quad d v=x d x \\ & \quad d u=\frac{1}{x} d x \quad v=\frac{x^{2}}{2} \\ & \text { } \\ & (\ln x)^{2} \frac{x^{2}}{2}-\left[\ln x \cdot \frac{x^{2}}{2}-\int \frac{x^{2}}{2} \frac{1}{x} d x\right] \\ & (\ln x)^{2} \frac{x^{2}}{2}-\left[\frac{\ln x \cdot x^{2}}{2}-\int \frac{x}{2} d x\right] \\ & \frac{x^{2}}{2}(\ln x)^{2}-\left[\frac{x^{2} \ln x}{2}-\frac{x^{2}}{4}\right]+C \\ & \text { } \\ & \frac{x^{2}}{2}(\ln x)^{2}-\frac{x^{2} \ln x}{2}+\frac{x^{2}}{4}+C \end{aligned} $$
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