Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 6 - Applications of Integration - 6.2 Regions Between Curves - 6.2 Exercises - Page 418: 41

Answer

$$A = \frac{1}{6}$$

Work Step by Step

$$\eqalign{ & {\text{The region is given by }}y = {\left( {x - 1} \right)^2}{\text{ and }}y = 7x - 19 \cr & {\text{Find the intersection points, let }}y = y \cr & {\left( {x - 1} \right)^2} = 7x - 19 \cr & {x^2} - 2x + 1 = 7x - 19 \cr & {x^2} - 9x + 20 = 0 \cr & \left( {x - 5} \right)\left( {x - 4} \right) = 0 \cr & {x_1} = 5,\,\,\,{x_2} = 4 \cr & {\text{Where }}7x - 19 \geqslant {\left( {x - 1} \right)^2}{\text{ on the interval }}\left[ {4,5} \right] \cr & \cr & {\text{The area between the curves is given by}} \cr & A = \int_4^5 {\left[ {7x - 19 - {{\left( {x - 1} \right)}^2}} \right]} dx \cr & A = \int_4^5 {\left( {7x - 19 - {x^2} + 2x - 1} \right)} dx \cr & A = \int_4^5 {\left( {9x - {x^2} - 20} \right)} dx \cr & {\text{Integrate}} \cr & A = \left[ {\frac{{9{x^2}}}{2} - \frac{{{x^3}}}{3} - 20x} \right]_4^5 \cr & A = \left[ {\frac{{9{{\left( 5 \right)}^2}}}{2} - \frac{{{{\left( 5 \right)}^3}}}{3} - 20\left( 5 \right)} \right] - \left[ {\frac{{9{{\left( 4 \right)}^2}}}{2} - \frac{{{{\left( 4 \right)}^3}}}{3} - 20\left( 4 \right)} \right] \cr & A = - \frac{{175}}{6} + \frac{{88}}{3} \cr & A = \frac{1}{6} \cr} $$
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