\( \frac{a(x-y)}{5x^{2}y^{2}} \cdot \frac{5xy}{b(y-x)} = \frac{a(x-y)}{5x^{2}y^{2}} \cdot \frac{5xy}{-b(x-y)} = \frac{a(x-y)5xy}{5x^{2}y^{2}(-b)(x-y)} = \frac{5axy(x-y)}{-5bx y^{2}(x-y)} = -\frac{a}{by} \)
Ответ: $$-\frac{a}{by}$$