Intermediate Algebra (6th Edition)

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

Practice Final Exam - Page 706: 59

Answer

$x=\dfrac{43}{21}$

Work Step by Step

Using the properties of logarithms, the given equation, $ \log_4(x+1)-\log_4(x-2)=3 ,$ is equivalent to \begin{array}{l}\require{cancel} \log_4\dfrac{x+1}{x-2}=3 .\end{array} Since $y=b^x$ is equivalent to $\log_by=x$, the equation aboveis equivalent to \begin{array}{l}\require{cancel} \dfrac{x+1}{x-2}=4^3 .\end{array} Using the properties of equality, the solution to the equation, $ \dfrac{x+1}{x-2}=4^3 ,$ is \begin{array}{l}\require{cancel} \dfrac{x+1}{x-2}=64 \\\\ x+1=64(x-2) \\\\ x+1=64x-128 \\\\ x-64x=-128-1 \\\\ -63x=-129 \\\\ x=\dfrac{-129}{-63} \\\\ x=\dfrac{129}{63} \\\\ x=\dfrac{\cancel{3}\cdot43}{\cancel{3}\cdot21} \\\\ x=\dfrac{43}{21} .\end{array}
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