Calculus: Early Transcendentals 8th Edition

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

Chapter 7 - Review - Exercises - Page 538: 39

Answer

$$ \int_{0}^{1 / 2} \frac{x e^{2 x}}{(1+2 x)^{2}} d x=\frac{1}{8} e-\frac{1}{4}. $$ where $C$ is constant.

Work Step by Step

$$ \int_{0}^{1 / 2} \frac{x e^{2 x}}{(1+2 x)^{2}} d x $$ first, we integrate$ \int \frac{x e^{2 x}}{(1+2 x)^{2}} d x $ by parts, with $$ \left[\begin{array}{ll}{u=x e^{2 x},} & {d v=\frac{dx }{(1+2 x)^{2}}} \\ {d u=\left(x \cdot 2 e^{2 x}+e^{2 x} \cdot 1\right) d x, } & {v=-\frac{1}{2} \cdot \frac{1}{1+2 x}}\end{array}\right] $$ so $$ \begin{aligned} \int \frac{x e^{2 x}}{(1+2 x)^{2}} d x &=-\frac{1}{2} \cdot \frac{x e^{2 x}}{1+2 x}-\int\left[-\frac{1}{2} \cdot \frac{e^{2 x}(2 x+1)}{1+2 x}\right] d x \\ &=-\frac{x e^{2 x}}{4 x+2}+\frac{1}{2} \cdot \frac{1}{2} e^{2 x}+C \\ &=e^{2 x}\left(\frac{1}{4}-\frac{x}{4 x+2}\right)+C. \end{aligned} $$ Thus, $$ \begin{aligned} \int_{0}^{1 / 2} \frac{x e^{2 x}}{(1+2 x)^{2}} d x &=\left[e^{2 x}\left(\frac{1}{4}-\frac{x}{4 x+2}\right)\right]_{0}^{1 / 2} \\ &=e\left(\frac{1}{4}-\frac{1}{8}\right)-1\left(\frac{1}{4}-0\right) \\ &=\frac{1}{8} e-\frac{1}{4}. \end{aligned} $$ where $C$ is constant.
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