Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 1 - Section 1.12 - Modeling Variation - 1.12 Exercises - Page 127: 5

Answer

(a) $y$ is directly proportional to $x$ (b) $y$ is not proportional to $x$

Work Step by Step

RECALL: (i) If the quantities (or variables) $x$ and $y$ are related by the equation $y=kx$, then $y$ is directly proportional to $x$. (ii) If the quantities (or variables) $x$ and $y$ are related by the equation $y=\dfrac{k}{x}$, then $y$ is inversely proportional to $x$. (a) The given equation is in the same form as in (i) above so $y$ is directly proportional to $x$ (b) The given equation is not similar to the equations in (i) and (ii) above so $y$ is not proportional to $x$.
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