Answer
-3
Work Step by Step
We know that if $b\gt0$ and $b\ne1$, then $y=log_{b}x$ is equivalent to $x=b^{y}$ (where $x\gt0$ and $y$ is a real number).
Therefore, $log_{4}\frac{1}{64}=-3$, because $4^{-3}=\frac{1}{4^{3}}=\frac{1}{64}$.
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