3. Докажите тождество: x-3 7x-4 : 7x-4 x-4 * 9x-3x² = 2 x-4

$$\frac{x-3}{7x-4} : (\frac{7x-4}{x-4} * \frac{9x-3x^2}{1}) = \frac{x-3}{7x-4} : (\frac{7x-4}{x-4} * \frac{3x(3-x)}{1}) = \frac{x-3}{7x-4} : (\frac{7x-4}{x-4} * \frac{-3x(x-3)}{1}) = \frac{x-3}{7x-4} * \frac{x-4}{(7x-4) * (-3x(x-3))} = \frac{x-4}{(7x-4)^2 * (-3x)} = \frac{-(x-4)}{3x(7x-4)^2} $$

Ответ:$$\frac{-(x-4)}{3x(7x-4)^2} $$