$$\frac{x}{(a-b)^2} + \frac{2}{5(a-b)} = \frac{5x}{5(a-b)^2} + \frac{2(a-b)}{5(a-b)^2} = \frac{5x+2a-2b}{5(a-b)^2}$$
Ответ: $$\frac{5x+2a-2b}{5(a-b)^2}$$