Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 3 - Review Exercises - Page 513: 73

Answer

$ x\approx 1.10$

Work Step by Step

$ e^{2x}-e^{x}-6=0$ introduce a temporary variable, $ t=e^{x}$ and the equation is equivalent to $ t^{2}-t-6=0\quad $ ... factor the trinomial $(t+2)(t-3)=0$ Either $ t=-2$ or $ t=3$ Bring back x: Either $ e^{x}=-2$ or $ e^{x}=3$ $ e^{x}$ is never negative, so it can't be that $ e^{x}=-2$ This leaves: $ e^{x}=3\qquad $ ... apply $\ln $( ) to both sides $ x=\ln 3\qquad $... use calculator and round to two decimal places $ x\approx 1.10$
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