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: 58


$2;$ $\dfrac {-5}{2}$

Work Step by Step

$\log x+\log \left( 2x+1\right) =1\Rightarrow \log _{10}\left[ x\left( 2x+1\right) \right] =1$ $\Rightarrow 2x^{2}+x=10^{1}\Rightarrow 2x^{2}+x-10=0$ $\Rightarrow x_{1},2=\dfrac {-b\pm \sqrt {b^{2}-4ac}}{2a}=\dfrac {-1\pm \sqrt {1^{2}-4\times 2\times \left( -10\right) }}{2\times 2}=\dfrac {-1\pm 9}{4}=2;\dfrac {-5}{2}$
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