Решение:
(x⁻¹ - y⁻¹) ⋅ (x - y)⁻¹ = $$\left(\frac{1}{x} - \frac{1}{y}\right) \cdot \frac{1}{x - y}$$ = $$\frac{y - x}{xy} \cdot \frac{1}{x - y}$$ = $$\frac{-(x - y)}{xy} \cdot \frac{1}{x - y}$$ = $$\frac{-1}{xy}$$.
Ответ: $$\frac{-1}{xy}$$