Calculus 8th Edition

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

Chapter 4 - Integrals - 4.4 Indefinite Integrals and the Net Change Theorem - 4.4 Exercises - Page 337: 39


$\displaystyle \frac{5}{2}$

Work Step by Step

$\displaystyle \int_2^5|x-3|dx$ Since the graph of $y=x-3$ is negative for $x<3$, we must split this integral into two parts to assure that we are getting the absolute value of $y=x-3$ $\displaystyle -\int_2^3(x-3)dx+\int_3^5(x-3)dx$ The reason why the first integral is negative is because we need to subtract out the negative area, thus we are taking the "absolute value" since we are adding the area both under the $x$-axis(from $x=2$ to $x=3$) and above (from $x=3$ to $x=5$). Now we evaluate: $\displaystyle -(\frac{x^2}{2}-3x)|_2^3+(\frac{x^2}{2}-3x)|_3^5$ $\displaystyle -([\frac{(3)^2}{2}-3(3)]-[\frac{(2)^2}{2}-3(2)])+([\frac{(5)^2}{2}-3(5)]-[\frac{(3)^2}{2}-3(3)])$ $\displaystyle -([\frac{9}{2}-9]-[\frac{4}{2}-6])+([\frac{25}{2}-15]-[\frac{9}{2}-9])$ $\displaystyle -([-\frac{9}{2}]-[-4])+([\frac{25}{2}-\frac{30}{2}]-[-\frac{9}{2}])$ $\displaystyle -(-\frac{9}{2}+4)+(-\frac{5}{2}+\frac{9}{2})$ $\displaystyle -(-\frac{1}{2})+(\frac{4}{2})$ $\displaystyle \frac{1}{2}+2$ $\displaystyle \frac{5}{2}$
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