Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 4 - Section 4.1 - Exponential Functions - 4.1 Exercises - Page 337: 45

Answer

(a) Please see graphs and explanations below. (b) $1.2$ and $22.4$

Work Step by Step

(a) First, we compare the rates of growth by graphing the functions $f(x)=2^x$ and $g(x)=x^5$ on the same set of axes as shown in the figures. (i) This small view window shows the first intersection of the two curves at $(1.2,2.3)$ which gives the first solution of the equation in (b). In this window, the rate of change for $g(x)$ is higher after the first intersection point. (ii) in this enlarged view window, the second intersection at $(22.4,5.7\times10^6)$ can be found. The rate of change for $f(x)$ appeared to be higher after $x=20$. (iii) in this wide overview window for the two functions, $f(x)$ clearly wins the race of rate of change indicated by its much faster growth rate in the vertical direction. (b) The solutions of the equation $2^x = x^5$ have been found from above (i) and (ii) to be $1.2$ and $22.4$ (rounded to one decimal place).
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