Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 7 - Principles Of Integral Evaluation - 7.2 Integration By Parts - Exercises Set 7.2 - Page 498: 28

Answer

$$ - \frac{6}{{25{e^5}}} + \frac{1}{{25}}$$

Work Step by Step

$$\eqalign{ & \int_0^1 {x{e^{ - 5x}}} dx \cr & {\text{substitute }}u = x,{\text{ }}du = dx \cr & dv = {e^{ - 5x}}dx,{\text{ }}v = - \frac{1}{5}{e^{ - 5x}} \cr & {\text{applying integration by parts}}{\text{, we have}} \cr & \int_0^1 {x{e^{ - 5x}}} dx = \left. {\left( { - \frac{1}{5}x{e^{ - 5x}}} \right)} \right|_0^1 - \int_0^1 {\left( { - \frac{1}{5}{e^{ - 5x}}} \right)dx} \cr & \int_0^1 {x{e^{ - 5x}}} dx = \left. {\left( { - \frac{1}{5}x{e^{ - 5x}}} \right)} \right|_0^1 + \frac{1}{5}\int_0^1 {{e^{ - 5x}}dx} \cr & {\text{integrating}} \cr & \int_0^1 {x{e^{ - 5x}}} dx = \left. {\left( { - \frac{1}{5}x{e^{ - 5x}}} \right)} \right|_0^1 - \frac{1}{{25}}\left. {\left( {{e^{ - 5x}}} \right)} \right|_0^1 \cr & \int_0^1 {x{e^{ - 5x}}} dx = \left. {\left( { - \frac{1}{5}x{e^{ - 5x}} - \frac{1}{{25}}{e^{ - 5x}}} \right)} \right|_0^1 \cr & {\text{evaluate limits}} \cr & = \left( { - \frac{1}{5}\left( 1 \right){e^{ - 5\left( 1 \right)}} - \frac{1}{{25}}{e^{ - 5\left( 1 \right)}}} \right) - \left( { - \frac{1}{5}\left( 0 \right){e^{ - 5\left( 0 \right)}} - \frac{1}{{25}}{e^{ - 5\left( 0 \right)}}} \right) \cr & {\text{simplify}} \cr & = \left( { - \frac{1}{5}{e^{ - 5}} - \frac{1}{{25}}{e^{ - 5}}} \right) - \left( { - \frac{1}{{25}}} \right) \cr & = - \frac{6}{{25{e^5}}} + \frac{1}{{25}} \cr} $$
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