College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 6 - Section 6.6 - Logarithmic and Exponential Equations - 6.6 Assess Your Understanding - Page 466: 83

Answer

The solution set is $\{1\}$

Work Step by Step

Use the hint, apply $\displaystyle \log_{a}M=\frac{\log_{b}M}{\log_{b}a}$ $\displaystyle \log_{4}x=\frac{\log_{2}x}{\log_{2}4}=\frac{\log_{2}x}{\log_{2}2^{2}}=\frac{\log_{2}x}{2}$ The equation becomes $\displaystyle \log_{2}(x+1)-\frac{1}{2}\log_{2}x=\log_{2}2 \quad $... multiply with 2 Before continuing, the restrictions on x are $\left\{\begin{array}{l} x+1 \gt 0\\ x \gt 0 \end{array}\right.\Rightarrow x \gt 0\qquad(*)$ otherwise the equation is undefined (because of the logarithmic functions) $2\log_{2}(x+1)-\log_{2}x=2\log_{2}2$ $\quad $...Apply$: \quad \log_{a}M^{r}=r\log_{a}M\quad $ $\log_{2}(x+1)^{2}-\log_{2}x=\log_{2}2^{2}$ $\quad $ ...Apply$: \displaystyle \quad \log_{a}\left(\frac{M}{N}\right)=\log_{a}M-\log_{a}N$ $\displaystyle \log_{2}\left(\frac{(x+1)^{2}}{x}\right)=\log_{2}4 \quad $...Apply$: \quad $If $\log_{a}M=\log_{a}N,$ then $M=N$ $\displaystyle \frac{(x+1)^{2}}{x}=4 \quad $...multiply with x $x^{2}+2x+1=4x$ $x^{2}-2x+1=0$ $(x-1)^{2}=0$ $ x=1\qquad$ so the solution set is $\{1\}$
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