Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 12 - Exponential Functions and Logarithmic Functions - 12.3 Logarithmic Functions - 12.3 Exercise Set - Page 803: 92

Answer

The two problems are equivalent - they are equally "easy" or "hard". In either case, we are seeking the exponent x by which 9 must be raised in order to obtain $\displaystyle \frac{1}{3}.$ This is because we use the definition of logarithm to rewrite a logarithmic equation as an equivalent exponential equation or the other way around: $m=\log_{a}x$ is equivalent to $a^{m}=x.$ Here, because $3^{2}=9\displaystyle \ \Rightarrow\ 3=9^{1/2}\ \Rightarrow\ \frac{1}{3}=9^{-1/2}$, we have $x=-\displaystyle \frac{1}{2}$, as $9^{-1/2}=\displaystyle \frac{1}{3}$, or, equivalently, $\displaystyle \log_{9}(9^{-1/2})=-\frac{1}{2}$.

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