Деление дробей

1. a) $$\frac{-3a^3}{2b^2} : \left( \frac{-a}{4b^2} \right) = \frac{-3a^3}{2b^2} \cdot \frac{4b^2}{-a} = \frac{-3a^3 \cdot 4b^2}{2b^2 \cdot (-a)} = \frac{-12a^3b^2}{-2ab^2} = 6a^2$$

   Ответ: $$6a^2$$

2. б) $$\frac{9m^2 - n^2}{n^2} : (15m + 5n) = \frac{(3m-n)(3m+n)}{n^2} : 5(3m+n) = \frac{(3m-n)(3m+n)}{n^2} \cdot \frac{1}{5(3m+n)} = \frac{(3m-n)(3m+n)}{5n^2(3m+n)} = \frac{3m-n}{5n^2}$$

   Ответ: $$\frac{3m-n}{5n^2}$$