Заменяем p(x) на 4x-4:
3(4x-4-1)-(4x-4)(3x) =
= 3(4x-5) - (12x^2 - 12x) =
= 12x - 15 - 12x^2 + 12x =
= -12x^2 + 12x + 12x - 15 =
= -12x^2 + 24x - 15.