Answer
$\frac{1}{y^{10}}$
Work Step by Step
Use the negative exponent rule: $x^{-y}$ = $\frac{1}{x^{y}}$ to bring the -4 underneath the fraction line: $\frac{1}{y^{4} y^{6}}$
Use the exponent product rule: $x^{y}$ $\times$ $x^{z}$ = $x^{y+z}$ to get $\frac{1}{y^{10}}$
