Answer
$\displaystyle \frac{a+b}{ab}$
Work Step by Step
$a^{-1}+b^{-1}$=.........$\displaystyle \frac{1}{a^{n}}=a^{-n}$ ........
$=\displaystyle \frac{1}{a}+\frac{1}{b}$ =......... common denominator: ab ....
$=\displaystyle \frac{b}{ab}+\frac{a}{ab}$
$=\displaystyle \frac{b+a}{ab}$
