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: 8

Answer

$\dfrac{\partial f}{\partial u}=2 e^{2u+2v}+2u+2v$

Work Step by Step

We have $\dfrac{\partial f}{\partial x}=2x; \dfrac{\partial f}{\partial y}=2y; \dfrac{\partial x}{\partial u}=e^{u+v}; \dfrac{\partial y}{\partial u}=1$ We apply the chain rule to obtain: $\dfrac{\partial f}{\partial u}=\dfrac{\partial f}{\partial x} \dfrac{\partial x}{\partial u}+\dfrac{\partial f}{\partial y} \dfrac{\partial y}{\partial u} \\=2x (e^{u+v})+2y(1)$ We are given that $x=e^{u+v}; y=u+v$ Thus, $\dfrac{\partial f}{\partial u}=2 e^{u+v} \ e^{u+v}+2 (u+v)$ Therefore, we get $\dfrac{\partial f}{\partial u}=2 e^{2u+2v}+2u+2v$
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