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: 29

Answer

0

Work Step by Step

Let \[I=\int_{-3}^{3}\frac{x}{1+|x|}dx\] For $x<0 , |x|=-x\;\; $ and $\;\;x\geq 0 , |x|=x$ \[I=\int_{-3}^{0}\frac{x}{1-x}dx+\int_{0}^{3}\frac{x}{1+x}dx\;\;\;\ldots (1)\] Let \[I_1=\int_{-3}^{0}\frac{x}{1-x}dx\] \[I_1=\int_{-3}^{0}\frac{1-(1-x)}{1-x}dx\] \[I_1=\int_{-3}^{0}\left(\frac{1}{1-x}-1\right)dx\] \[I_1=\left[-\ln|1-x|-x\right]_{-3}^{0}\] \[I_1=-[-\ln 4+3]=\ln 4-3\;\;\;\ldots (2)\] Let \[I_2=\int_{0}^{3}\frac{x}{1+x}dx\] \[I_2=\int_{0}^{3}\left(\frac{(1+x)-1}{1+x}\right)dx\] \[I_2=\int_{0}^{3}\left(1-\frac{1}{1+x}\right)dx\] \[I_2=\left[x-\ln|1+x|\right]_{0}^{3}\] \[I_2=3-\ln 4\;\;\;\ldots (3)\] Using (2), (3) in (1) \[I=(\ln 4-3)+(3-\ln 4)=0\] Hence $I=0.$
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