#### Answer

$log_2{\frac{1}{16}}=-4$

#### Work Step by Step

From the definition of the logarithmic function on page 456, we know that $b^{y}=x$ is equivalent to $y=log_b{x}$ (for $x\gt0$, $b\gt0$, and $b\ne1$).
Therefore, $2^{-4}=\frac{1}{16}$ is equivalent to $log_2{\frac{1}{16}}=-4$ in logarithmic form.