Answer
$\frac{y(xy-9)}{x^2y^2-9}$
Work Step by Step
Multiply $\frac{y^2}{y^2}$ to the expression, we have:
$\frac{x-9y^{-1}}{(x-3y^{-1})(x+3y^{-1})}=\frac{y^2}{y^2}\cdot\frac{x-9y^{-1}}{(x-3y^{-1})(x+3y^{-1})}=\frac{y(xy-9)}{(xy-3)(xy+3)}=\frac{y(xy-9)}{x^2y^2-9}$
