Answer
$\frac{3}{64}$
Work Step by Step
We know that $a^{−n}=\frac{1}{a^{n}}$ and $\frac{1}{a^{-n}}=a^{n}$ (as long as a is a nonzero real number and n is an integer).
Therefore, $4^{-2}-4^{-3}=\frac{1}{4^{2}}-\frac{1}{4^{3}}=\frac{1}{16}-\frac{1}{64}=\frac{1\times4}{16\times4}-\frac{1}{64}=\frac{4}{64}-\frac{1}{64}=\frac{4-1}{64}=\frac{3}{64}$.