б) $$ \frac{3-x}{(x-1)(x+1)} - \frac{x-2}{x(1-x)} = \frac{3-x}{(x-1)(x+1)} + \frac{x-2}{x(x-1)} = \frac{x(3-x) + (x-2)(x+1)}{x(x-1)(x+1)} = \frac{3x-x^2 + x^2 + x - 2x - 2}{x(x-1)(x+1)} = \frac{2x - 2}{x(x-1)(x+1)} = \frac{2(x-1)}{x(x-1)(x+1)} = \frac{2}{x(x+1)} $$
Ответ: $$ \frac{2}{x(x+1)} $$