College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 4, Exponential and Logarithmic Functions - Section 4.5 - Exponential and Logarithmic Functions - 4.5 Exercises - Page 404: 29


(a) $x=\frac{1-\ln 12}{4}$ (b) $x\approx -0.371227$

Work Step by Step

(a) We need to solve: $8+e^{1-4x}=20$ $e^{1-4x}=20-8=12$ We take the log of both sides and use log rules to simplify: $\ln e^{1-4x}=\ln 12$ $1-4x=\ln 12$ $x=\frac{1-\ln 12}{4}$ (b) We solve using a calculator: $x\approx -0.371227$
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