Functions Modeling Change: A Preparation for Calculus, 5th Edition

Published by Wiley
ISBN 10: 1118583191
ISBN 13: 978-1-11858-319-7

Chapter 2 - Functions - Review Exercises and Problems for Chapter Two - Page 109: 18

Answer

Domain: all real numbers, $q\neq 5 / 4$ Range: all real numbers, $s^{-1}(y)\neq -1/2$

Work Step by Step

Since division by 0 is undefined, $s(q)$ is not defined when $5-4 q=0$. So the domain of $s(q)$ is all real numbers except $q=5 / 4$. To find the range we find the inverse function. We solve the equation $y=s(q)=\frac{2 q+3}{5-4 q}$ for $q$. $$ \begin{aligned} y & =\frac{2 q+3}{5-4 q} \\ y(5-4 q) & =2 q+3 \\ 5 y-4 q y & =2 q+3 \\ 5 y-3 & =q(2+4 y) \\ q & =\frac{5 y-3}{2+4 y} \\ s^{-1}(y) & =\frac{5 y-3}{2+4 y} \end{aligned} $$ The domain of the inverse function is all real numbers except $-1 / 2$, so the range of $s(q)$ is all real numbers except $-1 / 2$.
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