Calculus with Applications (10th Edition)

Published by Pearson
ISBN 10: 0321749006
ISBN 13: 978-0-32174-900-0

Chapter 7 - Integration - 7.5 The Area Between Two Curves - 7.5 Exercises - Page 405: 9

Answer

$$A = \frac{4}{3}$$

Work Step by Step

$$\eqalign{ & y = {x^2},\,\,\,\,\,y = 2x \cr & {\text{Find the points of intersection of the graphs}} \cr & {x^2} = 2x \cr & {x^2} - 2x = 0 \cr & {\text{factor}} \cr & x\left( {x - 2} \right) = 0 \cr & x = 0{\text{ and }}x = 2 \cr & {\text{We have the interval }}\left( {0,2} \right) \cr & {\text{Evaluate both functions at }}x = 1 \cr & y\left( 1 \right) = {\left( 1 \right)^2} = 1 \cr & y\left( 2 \right) = 2\left( 1 \right) = 2 \cr & {\text{For the interval }}\left( {0,2} \right){\text{ we have that }}2x \geqslant {x^2} \cr & \cr & {\text{The area is given by}}: \cr & A = \int_0^2 {\left( {2x - {x^2}} \right)} dx \cr & {\text{Integrating}} \cr & A = \left( {{x^2} - \frac{{{x^3}}}{3}} \right)_0^2 \cr & A = \left( {{{\left( 2 \right)}^2} - \frac{{{{\left( 2 \right)}^3}}}{3}} \right) - \left( {{{\left( 0 \right)}^2} - \frac{{{{\left( 0 \right)}^3}}}{3}} \right) \cr & A = \left( {\frac{4}{3}} \right) - \left( 0 \right) \cr & A = \frac{4}{3} \cr} $$
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