11. \(\frac{x^3(x-4)}{(x-3)(x-4)}=\)

Сокращаем на \(x-4\): \(\frac{x^3(x-4)}{(x-3)(x-4)}=\frac{x^3}{x-3}\), \(x\ne3,4\).

Ответ: \(\frac{x^3}{x-3}\)