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: 20

Answer

$t=\dfrac{\log5}{10\log1.375}\approx0.505391$

Work Step by Step

$10(1.375)^{10t}=50$ Take the factor $10$ to divide the right side of the equation: $1.375^{10t}=\dfrac{50}{10}$ $1.375^{10t}=5$ Apply $\log$ to both sides of the equation: $\log1.375^{10t}=\log5$ Using the power of a power rule, the left side of the equation can be rewritten like this: $\log(1.375^{10})^{t}=\log5$ Take down the exponent $t$ to multiply in front of the $\log$: $t\log(1.375)^{10}=\log5$ Solve for $t$: $t=\dfrac{\log5}{\log(1.375)^{10}}=\dfrac{\log5}{10\log1.375}\approx0.505391$
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