Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 8 Rational Functions - 8.1 Model Inverse and Joint Variation - Guided Practice for Examples 5 and 6 - Page 554: 11


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Work Step by Step

The general equation for joint variation is: $z=axy$ where $a$ is some constant. Then plugging in the given values for $z,x,y$ we get: $18=a(-2)(6)=-12a\\a=-1.5$. Thus the model is: $z=-1.5xy$. Then plugging in $x=-2,y=5$: $z=-1.5(-2)(5)=15$
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