2) a²b/(a-b) * (1/b - 1/a);

2) $$\frac{a^2b}{a-b} \cdot (\frac{1}{b} - \frac{1}{a}) = \frac{a^2b}{a-b} \cdot (\frac{a - b}{ab}) = \frac{a^2b(a-b)}{(a-b)ab} = \frac{a^2b}{ab} = a$$

Ответ: $$a$$