Answer
$\frac{1}{y^{10}}$
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, $\frac{y^{-4}}{y^{6}}=\frac{1}{y^{4}}\times\frac{1}{y^{6}}=\frac{1}{y^{4+6}}=\frac{1}{y^{10}}$.
