Calculus: Early Transcendentals (2nd Edition)

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

Chapter 12 - Functions of Several Veriables - 12.4 Partial Derivatives - 12.4 Exercises - Page 904: 29

Answer

$${h_{xx}}\left( {x,y} \right) = 6x,\,\,\,\,\,\,\,\,{\text{ }}{h_{yy}}\left( {x,y} \right) = 2x,\,\,\,\,\,\,\,{h_{xy}}\left( {x,y} \right) = 2y{\text{ and }}{h_{yx}}\left( {x,y} \right) = 2y$$

Work Step by Step

$$\eqalign{ & h\left( {x,y} \right) = {x^3} + x{y^2} + 1 \cr & {\text{Find the first partial derivatives }}{h_x}\left( {x,y} \right){\text{ and }}{h_y}\left( {x,y} \right){\text{ then}} \cr & {h_x}\left( {x,y} \right) = \frac{\partial }{{\partial x}}\left[ {{x^3} + x{y^2} + 1} \right] \cr & {\text{treat }}y{\text{ as a constant}}{\text{, then}} \cr & {h_x}\left( {x,y} \right) = 3{x^2} + {y^2} \cr & and \cr & {h_y}\left( {x,y} \right) = \frac{\partial }{{\partial y}}\left[ {{x^3} + x{y^2} + 1} \right] \cr & {\text{treat }}x{\text{ as a constant}}{\text{, then }} \cr & {h_y}\left( {x,y} \right) = 2xy \cr & \cr & {\text{Find the second partial derivatives }}{h_{xy}}\left( {x,y} \right){\text{ and }}{h_{yx}}\left( {x,y} \right){\text{ then}} \cr & {h_{xy}}\left( {x,y} \right) = \frac{\partial }{{\partial y}}\left[ {3{x^2} + {y^2}} \right] \cr & {h_{xy}}\left( {x,y} \right) = 2y \cr & and \cr & {\text{ }}{h_{yx}}\left( {x,y} \right) = \frac{\partial }{{\partial x}}\left[ {2xy} \right] \cr & {\text{ }}{h_{yx}}\left( {x,y} \right) = 2y \cr & \cr & {\text{Find the second partial derivatives }}{h_{xx}}\left( {x,y} \right){\text{ and }}{h_{yy}}\left( {x,y} \right){\text{ then}} \cr & {h_{xx}}\left( {x,y} \right) = \frac{\partial }{{\partial x}}\left[ {3{x^2} + {y^2}} \right] \cr & {h_{xx}}\left( {x,y} \right) = 6x \cr & and \cr & {\text{ }}{h_{yy}}\left( {x,y} \right) = \frac{\partial }{{\partial y}}\left[ {2xy} \right] \cr & {\text{ }}{h_{yy}}\left( {x,y} \right) = 2x \cr} $$
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