Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 4 - Section 4.5 - Exponential and Logarithmic Functions - 4.5 Exercises - Page 368: 49

Answer

$x=5$

Work Step by Step

$\log x+\log(x-1)=\log(4x)$ Combine the sum of logarithms present on the left side of the equation as a product: $\log x(x-1)=\log(4x)$ Since $\log$ is one to one, this equation becomes: $x(x-1)=4x$ Solve for $x$: $x^{2}-x-4x=0$ $x^{2}-5x=0$ $x(x-5)=0$ The solutions are: $x=0$ and $x=5$ Verify the solutions: $x=5$ True $x=0$ False The final answer: $x=5$
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