Algebra 2 Common Core

Published by Prentice Hall
ISBN 10: 0133186024
ISBN 13: 978-0-13318-602-4

Chapter 7 - Exponential and Logarithmic Functions - 7-5 Exponential and Logarithmic Equations - Practice and Problem-Solving Exercises - Page 473: 45

Answer

$x=7$

Work Step by Step

Recall the quotient property of a logarithm (pg. 462): $\log_b{\frac{m}{n}}=\log_b{m}-\log_b{n}$ Also, recall the definition of a logarithm (pg. 451): $\log_{b}{x}=y$ iff $b^y=x$ We are asked to solve: $\log(7x+1)=\log(x-2)+1$ $\log(7x+1)-\log(x-2)=1$ We apply the quotient property: $\log_{10}\frac{7x+1}{x-2}=1$ Next, we apply the definition of a logarithm: $10^1=\frac{7x+1}{x-2}$ $10(x-2)=7x+1$ $10x-20=7x+1$ $10x-7x=1+20$ $3x=21$ $x=21/3$ $x=7$ We confirm that the answer works: $\log(7\cdot7+1)=\log(7-2)+1$ $\log(50)=\log(5)+1$ $1.7=0.7+1$ $1.7=1.7$
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