Intermediate Algebra (12th Edition)

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

Chapter 9 - Review Exercises - Page 638: 54

Answer

$\left\{\dfrac{3}{8}\right\}$

Work Step by Step

Using the properties of equality, the given equation, $ \log(2x+3)=1+\log x $, is equivalent to \begin{align*}\require{cancel} \log(2x+3)-\log x&=1 .\end{align*} Using the properties of logarithms, the equation above is equivalent to \begin{align*}\require{cancel} \log\dfrac{2x+3}{x}&=1 &(\text{use }\log_b \dfrac{x}{y}=\log_b x-\log_b y) \\\\ \log_{10}\dfrac{2x+3}{x}&=1 &(\text{use }\log x=\log_{10} x) .\end{align*} Since $\log_b y=x$ implies $y=b^x$, the equation above implies \begin{align*}\require{cancel} \dfrac{2x+3}{x}&=10^1 \\\\ \dfrac{2x+3}{x}&=10 .\end{align*} Using the properties of equality, the equation above is equivalent to \begin{align*}\require{cancel} \cancel x\cdot\dfrac{2x+3}{\cancel x}&=10\cdot x \\\\ 2x+3&=10x \\ 3&=10x-2x \\ 3&=8x \\\\ \dfrac{3}{8}&=\dfrac{\cancel8x}{\cancel8} \\\\ \dfrac{3}{8}&=x .\end{align*} Hence, the solution set of the equation $ \log(2x+3)=1+\log x $ is $ \left\{\dfrac{3}{8}\right\} $.
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