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: 44

Answer

$\large\frac{40}{3}$

Work Step by Step

Let \[I=\int_{2}^{6}\frac{y}{\sqrt{y-2}}dy\] Clearly 2 is point of infinite discontinuity of integrand $\large\frac{y}{\sqrt{y-2}}$ \[\Rightarrow I=\lim_{t\rightarrow 2^+}\int_{t}^{6}\frac{y}{\sqrt{y-2}}dy\;\;\;\ldots (1)\] Let \[I_1=\int\frac{y}{\sqrt{y-2}}dy\] \[I_1=\int\frac{(y-2)+2}{\sqrt{y-2}}dy\] \[I_1=\int\left[\sqrt{y-2}+2(y-2)^{-\frac{1}{2}}\right]dy\] \[I_1=\frac{2(y-2)^{\frac{3}{2}}}{3}+2(2)(y-2)^{\frac{1}{2}}+C\] Where $C$ is constant of integration \[I_1=\frac{2(y-2)^{\frac{3}{2}}}{3}+4\sqrt{y-2}+C\;\;\;\ldots (2)\] Using (2) in (1) \[I=\lim_{t\rightarrow 2^+}\left[\frac{2(y-2)^{\frac{3}{2}}}{3}+4\sqrt{y-2}\right]_{t}^{6}\] \[I=\lim_{t\rightarrow 2^+}\left[\frac{2}{3}(8)+4(2)-\frac{2(t-2)^{\frac{3}{2}}}{3}-4\sqrt{t-2}\right]\] \[I=\frac{16}{3}+8=\frac{40}{3}\] Since limit on R.H.S. of (1) exists so $I$ is convergent and $I=\large\frac{40}{3}$.
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