Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 5: Integrals - Section 5.6 - Definite Integral Substitutions and the Area Between Curves - Exercises 5.6 - Page 304: 55

Answer

$\displaystyle \frac{8}{3}$

Work Step by Step

Rewrite the equations as functions of y: $\left[\begin{array}{lll} x+y^{2}=0 & ... & x+3y^{2}=2\\ x=-y^{2} & & x=2-3y^{2}\\ & & \end{array}\right]$ Graphing the given equations, we find the intersections or we solve the equation $f(y)=g(y), $ where $ f(y)=2-3y^{2} \quad$ (the curve on the right side) and $ g(y)=-y^{2}\quad$ (the curve on the left). When $y\in[c,d]=[-1,1]$, the area between the graphs is $A=\displaystyle \int_{c}^{d} [f(y)-g(y)]dy=\displaystyle \int_{-1}^{1}[2-3y^{2}-(-y^{2})]dy$ $=\displaystyle \int_{-1}^{1}[2-2y^{2}]dy$ $=\displaystyle \left[2y-\frac{2y^{3}}{3} \right]_{-1}^{1}$ $=2(1+1)-\displaystyle \frac{2(1+1)}{3}$ $=\displaystyle \frac{8}{3}$
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