(2х-5) (в кубе)- 2х(2х-1)(2х-1)
(2х-5)^3-2x*(2x-1)*(2x-1)=(2x-5)*(2x-5)*(2x-5)-2x*(2x-1)*(2x-1)=(4x^2-10x-10x+25)*(2x-5)-2x*(4x^2-2x-2x+1)=(4x^2-20x+25)*(2x-5)-2x*(4x^2-4x+1)=(8x^3-40x^2+50x-20x^2+100x-125)-(8x^3-8x^2+2x)=8x^3-60x^2+150x-125-8x^3-8x^2+2x=-68x^2+152x-125