Multivariable Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 0-53849-787-4
ISBN 13: 978-0-53849-787-9

Chapter 14 - Partial Derivatives - 14.5 Exercises - Page 955: 34

Answer

$z_x=\dfrac{\ln y}{2z-y}$ and $z_y=\dfrac{zy+x}{2yz-y^2}$

Work Step by Step

We are given: $yz+x \ln y=z^2$ Re-arrange as: $yz+x \ln y-z^2=0$ Consider $F(x,y,z)=yz+x \ln y-z^2=0$ $F_x=\ln y$ and $F_y=z+xy^{-1}$ and $F_z=y-2z$ Use Equation 7: $z_x=-\dfrac{F_x}{F_z}$ and $z_y=-\dfrac{F_y}{F_z}$ $z_x=-\dfrac{F_x}{F_z}=-\dfrac{\ln y}{y-2z}$ and $z_y=-\dfrac{F_y}{F_z}=-\dfrac{z+xy^{-1}}{y-2z}$ Hence, we have $z_x=\dfrac{\ln y}{2z-y}$ and $z_y=\dfrac{zy+x}{2yz-y^2}$
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