574. Сократите дробь: a) $$\frac{8a^3 - 27}{9 - 12a + 4a^2}$$; б) $$\frac{ax - 2x - 4a + 8}{3a - 6 - ax + 2x}$$.

a) $$\frac{8a^3 - 27}{9 - 12a + 4a^2} = \frac{(2a)^3 - 3^3}{(2a - 3)^2} = \frac{(2a - 3)(4a^2 + 6a + 9)}{(2a - 3)^2} = \frac{4a^2 + 6a + 9}{2a - 3}$$ б) $$\frac{ax - 2x - 4a + 8}{3a - 6 - ax + 2x} = \frac{x(a - 2) - 4(a - 2)}{3(a - 2) - x(a - 2)} = \frac{(a - 2)(x - 4)}{(a - 2)(3 - x)} = \frac{x - 4}{3 - x}$$