Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 15 - Differentiation in Several Variables - 15.6 The Chain Rule - Exercises - Page 808: 16

Answer

$$135e^{12}$$

Work Step by Step

Given $$h(u, v)=u e^{v}, \ \ \ u=q^{3},\ \ \ \ \ v=q r^{2}$$ Since at $(q,r)=(3,2)$; $(u,v)= ( 27,12)$ $$ \frac{\partial h}{\partial \:u}= e^{v},\ \ \ \ \ \frac{\partial h}{\partial \:v}=u e^{v} \\ \frac{\partial u}{\partial q}=3q^2,\ \ \ \ \ \ \ \ \ \ \ \frac{\partial v}{\partial q}=r^2 $$ Then \begin{align*} \frac{\partial h }{ \partial u}&=\frac{\partial h }{ \partial u}\frac{\partial u }{ \partial q}+\frac{\partial h }{ \partial v}\frac{\partial v }{ \partial q}\\ &= 3q^2e^v+ur^2e^v \\ &=3q^2e^{qr^2}+q^3r^2e^{qr^2} \end{align*} Hence \begin{align*} \frac{\partial h }{ \partial q}\bigg|_{(3,2)}&= 3(3)^2e^{(3)(2)^2}+(3)^3(2)^2e^{(3)(2)^2}\\ &=135e^{12} \end{align*}
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