Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 9 - Section 9.8 - Exponential and Logarithmic Equations and Problem Solving - Exercise Set - Page 591: 31

Answer

$x=\dfrac{1}{5}$

Work Step by Step

Using the properties of logarithms, the given expression, $ \ln5+\ln x=0 ,$ is equivalent to \begin{array}{l}\require{cancel} \ln(5\cdot x)=0 \\\\ \ln(5x)=0 \\\\ \log_e(5x)=0 .\end{array} Since $y=b^x$ is equivalent to $\log_b y=x$, then the solution to the equation, $ \log_e(5x)=0 ,$ is \begin{array}{l}\require{cancel} 5x=e^0 \\\\ 5x=1 \\\\ x=\dfrac{1}{5} .\end{array} Upon checking, $ x=\dfrac{1}{5} $ satisfies the original equation.
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