Algebra 2 Common Core

Published by Prentice Hall
ISBN 10: 0133186024
ISBN 13: 978-0-13318-602-4

Chapter 8 - Rational Functions - 8-1 Inverse Variation - Practice and Problem-Solving Exercises - Page 503: 8

Answer

direct variation; $y=2x$

Work Step by Step

Recall: (1) A direct variation is represented by the equation $y=kx$ where $k$ is the constant of variation. As the value of $x$ increases, the value of $y$ also increases. (2) An inverse variation is represented by the equation $xy=k$, where $k$ is the constant of variation. As the value of $x$ increases, the value of $y$ decreases. Notice that in the given table, as the value of $x$ increases, the value of $y$ also increases. This means that the table could involve a direct variation. Note further that for each value of $x$, the value of $y$ can be found by multiplying $2$ to the value of $x$. Thus, the given table involves a direct variation. The equation that models the direct variation can be determined by solving the value of $k$: This can be done by taking any ordered pair from the table, then substituting the values of $x$ and $y$ into the direct variation formula $y=kx$. Using $(11, 22)$: \begin{align*} y&=kx\\\\ 22&=k(11)\\\\ \frac{22}{11}&=\frac{k(11)}{11}\\\\ 2&=k \end{align*} Therefore, the equation that models the direct variation is $y=2x$.
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