А1. Сократите дробь: a) $$rac{5ab}{15b}$$; б) $$rac{6m(2-n)}{3m^2(n-2)}$$.

a) $$rac{5ab}{15b} = \frac{5 \cdot a \cdot b}{3 \cdot 5 \cdot b} = \frac{a}{3}$$
б) $$rac{6m(2-n)}{3m^2(n-2)} = \frac{2 \cdot 3 \cdot m \cdot (2-n)}{3 \cdot m \cdot m \cdot (n-2)} = \frac{2(2-n)}{m(n-2)} = \frac{-2(n-2)}{m(n-2)} = -\frac{2}{m}$$