Algebra 1: Common Core (15th Edition)

Published by Prentice Hall
ISBN 10: 0133281140
ISBN 13: 978-0-13328-114-9

Chapter 5 - Linear Functions - Chapter Review - Page 354: 15


The direct variation equation is $y = -x$. $y = -7$ when $x = 7$.

Work Step by Step

The equation for direct variation is given by the following formula: $y = kx$, where $k$ is the constant of variation. To write a direct variation equation, we must first find the constant of variation. Let's plug in the values for $x$ and $y$ that we are given: $-4 = k(4)$ Divide both sides by $4$ to solve for $k$: $k = -1$ The direct variation equation is $y = -x$. Now that we have the equation, to find $y$, we simply plug in the value we are given for $x$: $y = -(7)$ Multiply to simplify: $y = -7$
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