Simplify a−2−b−2a−1+b−1\frac{a^{-2}-b^{-2}}{a^{-1}+b^{-1}}a−1+b−1a−2−b−2.
b−aab\frac{b-a}{ab}abb−a
a−bab\frac{a-b}{ab}aba−b
a−ba-ba−b
1a−b\frac{1}{a-b}a−b1