2. Сократите дробь: a) 25a3 / 15a б) 8x-16y / 5x-10y в) y2-81 / 18+2y

a) $$\frac{25a^3}{15a} = \frac{5 \cdot 5 \cdot a \cdot a^2}{5 \cdot 3 \cdot a} = \frac{5a^2}{3}$$

б) $$\frac{8x-16y}{5x-10y} = \frac{8(x-2y)}{5(x-2y)} = \frac{8}{5}$$

в) $$\frac{y^2-81}{18+2y} = \frac{(y-9)(y+9)}{2(9+y)} = \frac{y-9}{2}$$

Ответ: a) $$\frac{5a^2}{3}$$, б) $$\frac{8}{5}$$, в) $$\frac{y-9}{2}$$