Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 3 - Linear and Quadratic Functions - 3.1 Properties of Linear Functions and Linear Models - 3.1 Assess Your Understanding - Page 128: 38


a) $\$18$; b) $x=64$ minutes; c) $x=173$ minutes; d) $[0,43200]$

Work Step by Step

We are given: $C(x)=0.26x+5$ a) Compute $C(50)$: $C(50)=0.26(50)+5$ $C(50)=18$ b) Solve the equation: $0.26x+5=21.64$ $0.26x+5-5=21.64-5$ $0.26x=16.64$ $x=\dfrac{16.64}{0.26}$ $x=64$ minutes c) Solve the inequality $C(x)\leq 50$ $0.26x+5\leq 50$ $0.26x+5-5\leq 50-5$ $0.26x\leq 45$ $x\leq\dfrac{45}{0.26}$ $x\leq 173.08$ $x=173$ minutes d) The implied domain of $C$ has the minimum 0 (when no calls are made) and the number of minutes in a month (if all minutes in a month are used): $[0,30\times 24\times 60]=[0,43200]$
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