90. Выполните действие: a) $$\frac{a^2}{ax - x^2} + \frac{x}{x-a}$$

a) $$\frac{a^2}{ax - x^2} + \frac{x}{x-a} = \frac{a^2}{x(a-x)} + \frac{x}{x-a} = \frac{a^2}{x(a-x)} - \frac{x}{a-x} = \frac{a^2 - x^2}{x(a-x)} = \frac{(a-x)(a+x)}{x(a-x)} = \frac{a+x}{x}$$