Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 9 - Section 9.5 - Exponential and Logarithmic Equations - Exercise Set - Page 727: 67

Answer

The solution set is $\{6\}$.

Work Step by Step

The given equation is $\log _3(x-5) +\log _3(x+3)=2$ Use product rule. $\log _3 [(x-5)(x+3)]=2$ Rewrite in exponential form. $(x-5)(x+3)= 3^2$ Use the distributive property on the left. $x^2+3x-5x-15=9$ Subtract $9$ from both sides. $x^2+3x-5x-15-9=9-9$ Simplify. $x^2-2x-24=0$ Factor. $x^2-6x+4x-24=0$ $x(x-6)+4(x-6)=0$ $(x-6)(x+4)=0$ Set both factors equal to $0$. $x-6=0$ or $x+4=0$ Isolate $x$. $x=6$ or $x=-4$ $-4$ is not in the domain of a logarithmic function. The solution is $x=6$.
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