Calculus 8th Edition

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

Chapter 5 - Applications of Integration - Review - Exercises - Page 393: 3

Answer

$\frac{7}{12}$

Work Step by Step

The area between two curves $y=f(x)$ and $y=g(x)$ between $x=a$ and $x=b$ is given by the formula: $$A=\int_a^b |f(x)-g(x)|dx.\quad\quad\quad(1)$$ Given $$f(x)=1-2 x^2, \quad g(x)=|x|$$ Since for $x>0$, $|x|= x$, find the intersection points \begin{aligned} 1-2x^2&= x\\ 2x^2+x-1&=0\\ (2x-1)(x+1)&=0 \end{aligned} Then $x=1/2,\ \ x=-1$, we refuse $x=-1<0$ By symmetry, we find the area between $a=0$, $a=1/2$ Since $ 1-2x^2\geq x $ for $0\leq x\leq 1/2$, then \begin{aligned} \text{Area} & =2 \int_0^{1 / 2}\left[\left(1-2 x^2\right)-x\right] d x\\ &=2 \int_0^{1 / 2}\left(-2 x^2-x+1\right) d x \\ & =2\left[-\frac{2}{3} x^3-\frac{1}{2} x^2+x\right]_0^{1 / 2}\\ &=2\left[\left(-\frac{1}{12}-\frac{1}{8}+\frac{1}{2}\right)-0\right] \\ & =2\left(\frac{7}{24}\right)\\ &=\frac{7}{12} \end{aligned}
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.