Question 13Assuming $a>b>0$, the expression $\frac{a^{-1}-b^{-1}}{a^{-2}-b^{-2}}$ can be written as$\frac{b-a}{ab}$$\frac{b+a}{ab}$$\frac{ab}{b+a}$$\frac{a^2-b^2}{a-b}$$a-b$