Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 8 - Integration Techniques, L'Hopital's Rule, and Improper Integrals - 8.2 Exercises - Page 522: 80

Answer

$$A = \frac{1}{{90}} + \frac{1}{{18}}{e^6}$$

Work Step by Step

$$\eqalign{ & y = \frac{1}{{10}}x{e^{3x}},{\text{ }}y = 0,{\text{ }}x = 0,{\text{ }}x = 2 \cr & {\text{From the graph we can define the area as}} \cr & A = \int_0^2 {\frac{1}{{10}}x{e^{3x}}} dx \cr & {\text{Integrating by parts}} \cr & u = \frac{1}{{10}}x,{\text{ }}du = \frac{1}{{10}}dx \cr & dv = {e^{3x}}dx.{\text{ }}v = \frac{1}{3}{e^{3x}} \cr & \int {udv = uv - \int {vdu} } \cr & \int {\frac{1}{{10}}x{e^{3x}}dx} = \left( {\frac{1}{3}{e^{3x}}} \right)\left( {\frac{1}{{10}}x} \right) - \int {\left( {\frac{1}{3}{e^{3x}}} \right)\left( {\frac{1}{{10}}} \right)dx} \cr & \int {\frac{1}{{10}}x{e^{3x}}dx} = \frac{1}{{30}}x{e^{3x}} - \frac{1}{{30}}\int {{e^{3x}}dx} \cr & \int {\frac{1}{{10}}x{e^{3x}}dx} = \frac{1}{{30}}x{e^{3x}} - \frac{1}{{90}}{e^{3x}} + C \cr & {\text{Therefore}} \cr & A = \int_0^2 {\frac{1}{{10}}x{e^{3x}}} dx \cr & A = \left[ {\frac{1}{{30}}x{e^{3x}} - \frac{1}{{90}}{e^{3x}}} \right]_0^2 \cr & A = \left[ {\frac{1}{{30}}\left( 2 \right){e^{3\left( 2 \right)}} - \frac{1}{{90}}{e^{3\left( 2 \right)}}} \right] - \left[ {\frac{1}{{30}}\left( 0 \right){e^{3\left( 0 \right)}} - \frac{1}{{90}}{e^{3\left( 0 \right)}}} \right] \cr & A = \frac{1}{{15}}{e^6} - \frac{1}{{90}}{e^6} + \frac{1}{{90}} \cr & A = \frac{1}{{90}} + \frac{1}{{18}}{e^6} \cr} $$
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