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: 40

Answer

$x=\ln3\approx1.098612$

Work Step by Step

$e^{2x}-e^{x}-6=0$ Let $e^{x}=u$ and $e^{2x}=u^{2}$ and rewrite the equation: $u^{2}-u-6=0$ Solve by factoring: $(u-3)(u+2)=0$ We get two solutions, which are: $u=3$ and $u=-2$ Let's undo the initial substitution, knowing that $u=e^{x}$. The solutions then become: $e^{x}=3$ and $e^{x}=-2$ Solve for $x$: $x=\ln3\approx1.098612$ The other equation has no real solution.
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