Multivariable Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 0-53849-787-4
ISBN 13: 978-0-53849-787-9

Chapter 11 - Multiple Integrals - 15.2 Exercises - Page 1011: 11

Answer

$\displaystyle \frac{31}{30}$

Work Step by Step

$\displaystyle \int_{0}^{1}\int_{0}^{1}v(u+v^{2})^{4}dudv$ = $\displaystyle \int_{0}^{1}[\int_{0}^{1}v(u+v^{2})^{4}du]dv$ = $\left[\begin{array}{l} t=u+v^{2}\\ dt=du \end{array}\right]$ = ... treat v as a constant in the inner integral. $\displaystyle \int_{0}^{1}[v\int_{v^{2}}^{v^{2}+1}t^{4}dt]dv$ $=\displaystyle \int_{0}^{1}[\frac{vt^{5}}{5}]_{t=v^{2}}^{t=v^{2}+1}dv$ $=\displaystyle \frac{1}{5}\int_{0}^{1}v [(v^{2}+1)^{5}-(v^{2})^{5}]dv$ $=\displaystyle \frac{1}{5}\int_{0}^{1}[v(1+v^{2})^{5}-v^{11}]dv$ $=\displaystyle \frac{1}{5}[\int_{0}^{1}v(1+v^{2})^{5}dv-\int_{0}^{1}v^{11}dv]$ ... for the first integral: $\left[\begin{array}{ll} t=1+v^{2} & \\ dt=2vdv & \\ v=0\Rightarrow t=1, & v=1\Rightarrow t=2 \end{array}\right]$ $=\displaystyle \frac{1}{5}\{\int_{1}^{2}\frac{1}{2}t^{5}dt-[\frac{v^{12}}{12}]_{0}^{1}\}$ $=\displaystyle \frac{1}{5}\{\frac{1}{2} [ \displaystyle \frac{t^{6}}{6}]_{1}^{2}-\frac{1-0}{12}\}$ $=\displaystyle \frac{1}{5}\{\frac{64-1}{12}-\frac{1}{12}\}$ $=\displaystyle \frac{62}{5\cdot 12}$ $=\displaystyle \frac{31}{30}$
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