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: 52

Answer

$$A = \frac{{19}}{6}$$

Work Step by Step

$$\eqalign{ & {\text{The intersection point between }}y = 4\sqrt {2x} {\text{ and }}y = - 4x + 6,{\text{ is}} \cr & 4\sqrt {2x} = - 4x + 6 \cr & 2\sqrt {2x} = - 2x + 3 \cr & 4\left( {2x} \right) = 9 - 12x + 4{x^2} \cr & 8x = 9 - 12x + 4{x^2} \cr & 4{x^2} - 20x + 9 = 0 \cr & \left( {2x - 9} \right)\left( {2x - 1} \right) = 0 \cr & {x_1} = \frac{9}{2},{\text{ }}{x_2} = \frac{1}{2} \cr & {\text{The intersection point between }}y = 2{x^2}{\text{ and }}y = - 4x + 6,{\text{ is}} \cr & 2{x^2} = - 4x + 6 \cr & 2{x^2} + 4x - 6 = 0 \cr & {x^2} + 2x - 3 = 0 \cr & \left( {x + 3} \right)\left( {x - 1} \right) = 0 \cr & {x_1} = - 3{\text{ and }}x = 1 \cr & {\text{The area of the region is given by:}} \cr & A = \int_{1/2}^1 {\left[ {4\sqrt {2x} - \left( { - 4x + 6} \right)} \right]} dx + \int_1^2 {\left( {4\sqrt {2x} - 2{x^2}} \right)} dx \cr & A = \int_{1/2}^1 {\left( {4\sqrt {2x} + 4x - 6} \right)} dx + \int_1^2 {\left( {4\sqrt {2x} - 2{x^2}} \right)} dx \cr & A = \left[ {\frac{{4\sqrt 2 }}{{3/2}}{x^{3/2}} + 2{x^2} - 6x} \right]_{1/2}^1 + \left[ {\frac{{4\sqrt 2 }}{{3/2}}{x^{3/2}} - \frac{{2{x^3}}}{3}} \right]_1^2 \cr & A = \left[ {\frac{{8\sqrt 2 }}{3}{x^{3/2}} + 2{x^2} - 6x} \right]_{1/2}^1 + \left[ {\frac{{8\sqrt 2 }}{3}{x^{3/2}} - \frac{{2{x^3}}}{3}} \right]_1^2 \cr & {\text{Evaluating}} \cr & A = \left( {\frac{{8\sqrt 2 - 12}}{3} + \frac{7}{6}} \right) + \left( {\frac{{16}}{3} - \frac{{8\sqrt 2 - 2}}{3}} \right) \cr & {\text{Simplifying}} \cr & A = \frac{{8\sqrt 2 - 12}}{3} + \frac{7}{6} + \frac{{16}}{3} - \frac{{8\sqrt 2 - 2}}{3} \cr & A = \frac{{19}}{6} \cr} $$
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