Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 4 - Inverse, Exponential, and Logarithmic Functions - 4.3 Logarithmic Functions - 4.3 Exercises - Page 447: 103

Answer

(a) $ -4$ (b) $ 6$ (c) $ 4$ (d) $-1$

Work Step by Step

Given $f(x)=log_ax$ and $f(3)=2$, we have $f(3)=log_a3=2$ and $a^2=3$, thus $a=3^{1/2}$. (a) $f(\frac{1}{9})=log_{3^{1/2}}(\frac{1}{9})=log_{3^{1/2}}(3^{-2})=\frac{-2}{1/2}=-4$ (b) $f(27)=log_{3^{1/2}}(27)=log_{3^{1/2}}(3^{3})=\frac{3}{1/2}=6$ (c) $f(9)=log_{3^{1/2}}(9)=log_{3^{1/2}}(3^{2})=\frac{2}{1/2}=4$ (d) $f(\frac{\sqrt 3}{3})=log_{3^{1/2}}(\frac{\sqrt 3}{3})=log_{3^{1/2}}(3^{-1/2})=\frac{-1/2}{1/2}=-1$
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