Calculus: Early Transcendentals (2nd Edition)

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

Chapter 13 - Multiple Integration - 13.1 Double Integrals over Rectangular Regions - 13.1 Exercises - Page 970: 8

Answer

$$\frac{{63}}{2}$$

Work Step by Step

$$\eqalign{ & \int_0^3 {\int_{ - 2}^1 {\left( {2x + 3y} \right)} } dxdy \cr & = \int_0^3 {\left[ {\int_{ - 2}^1 {\left( {2x + 3y} \right)} dx} \right]} dy \cr & {\text{solve the inner integral}}{\text{, treat }}y{\text{ as a constant}} \cr & \int_{ - 2}^1 {\left( {2x + 3y} \right)} dx = \left[ {{x^2} + 3xy} \right]_{ - 2}^1 \cr & {\text{evaluating the limits for }}x \cr & = \left[ {{{\left( 1 \right)}^2} + 3\left( 1 \right)y} \right] - \left[ {{{\left( { - 2} \right)}^2} + 3\left( { - 2} \right)y} \right] \cr & = \left( {1 + 3y} \right) - \left( {4 - 6y} \right) \cr & = 1 + 3y - 4 + 6y \cr & = 9y - 3 \cr & \cr & = \int_0^3 {\left[ {\int_{ - 2}^1 {\left( {2x + 3y} \right)} dx} \right]} dy \cr & = \int_0^3 {\left( {9y - 3} \right)} dy \cr & {\text{integrating}} \cr & = \left( {\frac{{9{y^2}}}{2} - 3y} \right)_0^3 \cr & = \left( {\frac{{9{{\left( 3 \right)}^2}}}{2} - 3\left( 3 \right)} \right) - \left( {\frac{{9{{\left( 0 \right)}^2}}}{2} - 3\left( 0 \right)} \right) \cr & {\text{simplifying}} \cr & = \frac{{81}}{2} - 9 \cr & = \frac{{63}}{2} \cr} $$
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