Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 4 - Section 4.3 - Logarithmic Functions - 4.3 Exercises - Page 352: 54

Answer

$y=\log_2{x}$

Work Step by Step

The graph contains the point $(\frac{1}{2}, -1)$. This means that the x and y-coordinates of this point satisfy the equation $y=\log_a{x}$. Substitute the x and y values into the given equation to obtain: $-1 = \log_a{(\frac{1}{2})}$ RECALL: $y=\log_a{x} \longrightarrow a^y=x$ Use the rule above to obtain: $-1 = \log_a{(\frac{1}{2})} \longrightarrow a^{-1} = \frac{1}{2}$ Note that $\frac{1}{2} = 2^{-1}$. So the expression above is equivalent to: $a^{-1} = 2^{-1}$ Use the rule $a^x = b^x \longrightarrow a = b$ to obtain: $a=2$ Thus, the equation of the function whose graph is given is $y=\log_2{x}$.
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