Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 4 - Inverse, Exponential, and Logarithmic Functions - 4.5 Exponential and Logarithmic Equations - 4.5 Exercises - Page 469: 78


$\dfrac {1\pm \sqrt {85}}{6}$

Work Step by Step

$\log _{5}\left( 3x+2\right) +\log _{5}\left( x-1\right) =1\Rightarrow \log _{5}\left( \left( 3x+2\right) \left( x-1\right) \right) =\log _{5}5$ $\left( 3x+2\right) \left( x-1\right) =5\Rightarrow 3x^{2}-x-2=5\Rightarrow 3x^{2}-x-7=0$ $x_{1,2}=\dfrac {-b\pm \sqrt {b^{2}-4ac}}{2a}=\dfrac {1\pm \sqrt {1-4\times 3\times \left( -7\right) }}{2\times 3}=\dfrac {1\pm \sqrt {85}}{6}$
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