Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 7 - Techniques of Integration - Review - Exercises - Page 578: 13

Answer

$$3\left(x^{2/3} e^{\sqrt[3]{x}}-2 \sqrt[3]{x}e^{\sqrt[3]{x}}+e^{\sqrt[3]{x}} \right)+c$$

Work Step by Step

Given $$\int e^{\sqrt[3]{x}} d x$$ Let $u^3=x\ \Rightarrow \ \ 3u^2 du=dx$, then $$ \int e^{\sqrt[3]{x}} d x=3\int u^2e^{u} d u$$ Integrate by parts \begin{align*} U&=u^2\ \ \ \ \ \ \ \ \ \ \ \ \ \ dv=e^udu\\ dU&=2udu\ \ \ \ \ \ \ \ \ \ \ \ \ dv= e^u \end{align*} \begin{align*} \int e^{\sqrt[3]{x}} d x&=3\int u^2e^{u} d u\\ &=3\left(u^2 e^u-2\int ue^udu \right) \end{align*} To compute $ \displaystyle\int ue^udu $ \begin{align*} U&=u \ \ \ \ \ \ \ \ \ \ \ \ \ \ dv=e^udu\\ dU&= du\ \ \ \ \ \ \ \ \ \ \ \ \ dv= e^u \end{align*} \begin{align*} \int ue^udu &=ue^u-\int e^udu\\ &=ue^u-e^u+c \end{align*} Hence \begin{align*} \int e^{\sqrt[3]{x}} d x&=3\int u^2e^{u} d u\\ &=3\left(u^2 e^u-2 ( ue^u-e^u) \right)+c\\ &=3\left(u^2 e^u-2 ue^u+e^u \right)+c\\ &=3\left(x^{2/3} e^{\sqrt[3]{x}}-2 \sqrt[3]{x}e^{\sqrt[3]{x}}+e^{\sqrt[3]{x}} \right)+c \end{align*}
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