Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 9 - Section 9.6 - Exponential and Logarithmic Equations; Further Applications - 9.6 Exercises - Page 630: 17

Answer

$x\approx261.291$

Work Step by Step

Taking the natural logarithm of both sides, the given equation, $ e^{0.012x}=23 $ is equivalent to \begin{align*}\require{cancel} \ln e^{0.012x}&=\ln23 .\end{align*} Using the properties of logarithms, the equation above is equivalent to \begin{align*}\require{cancel} 0.012x(\ln e)&=\ln23 &(\text{use }\log_b x^y=y\log_b x) \\ 0.012x(1)&=\ln23 &(\text{use }\ln e=1) \\ 0.012x&=\ln23 .\end{align*} Using the properties of equality, the equation above is equivalent to \begin{align*}\require{cancel} \dfrac{\cancel{0.012}x}{\cancel{0.012}}&=\dfrac{\ln23}{0.012} \\ x&=\dfrac{\ln23}{0.012} .\end{align*} Using a calculator, the approximate value of $ \ln23 $ is $ 3.1355 $. Thus, the equation above is equivalent to \begin{align*} x&=\dfrac{3.1355}{0.012} \\\\ x&=261.291 .\end{align*} Hence, the solution to the equation $ e^{0.012x}=23 $ is $ x\approx261.291 $.
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