Calculus 8th Edition

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

Chapter 7 - Techniques of Integration - 7.5 Strategy for Integration - 7.5 Exercises - Page 548: 63

Answer

\[2[x-2\sqrt x+2]e^{\sqrt x}\]

Work Step by Step

Let \[I=\int\sqrt x\:e^{\sqrt x}dx\;\;\;\ldots(1)\] Substitute $\sqrt x=t\;\;\;\ldots (2)$ \[\Rightarrow \frac{1}{2\sqrt x}dx=dt\] \[I=\int 2t^2e^t\:dt\] Using integration by parts \[I=2\left[t^2\int e^t dt-\int \left((t^2)'\int e^t dt\right)dt\right]+C\] Where $C$ is constant of integration \[I=2\left[t^2 e^t-2\int te^t dt\right]\;\;\;\ldots (3)\] Let \[I_1=\int te^tdt\] \[I_1=t\int e^tdt-\int \left((t)'\int e^tdt\right)dt\] \[I_1=te^t-\int e^tdt\] \[I_1=te^t-e^t\;\;\;\ldots (4)\] Using (4) in (3) \[I=2\left[t^2 e^t-2 te^t+2e^t\right]\] \[I=2[t^2-2t+2]e^t\] From (2) \[I=2[x-2\sqrt x+2]e^{\sqrt x}\] Hence, \[\;I=2[x-2\sqrt x+2]e^{\sqrt x}.\]
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