4. Найдите частное дробей: a) $$\frac{a^2b^4}{n^3} : \frac{a^3b^2}{n^2}$$ б) $$\frac{x^2-6x+9}{x+2} : \frac{x-3}{x^2-4}$$

a) $$\frac{a^2b^4}{n^3} : \frac{a^3b^2}{n^2} = \frac{a^2b^4}{n^3} \cdot \frac{n^2}{a^3b^2} = \frac{a^2b^4n^2}{n^3a^3b^2} = \frac{b^2}{an}$$ б) $$\frac{x^2-6x+9}{x+2} : \frac{x-3}{x^2-4} = \frac{(x-3)^2}{x+2} \cdot \frac{(x-2)(x+2)}{x-3} = (x-3)(x-2) = x^2 - 5x + 6$$