(1-2x)(4x^2+2x+1)+8x^3=1+4х^2+2х+1-2х^3+4x^2-2x+8x^3=2+6x^3
(2-x)(2+x)(x-1)+x^2(x-1)=(4+2x-2x-x^2)(x-1)+x^2(x-1)=4x+2x^3-2x^3-x^3-4-2x+2x+x^2+x^3-x=-4+4x+x^2
(x-5)^2-4(x+5)^2=(x-5)(x-5)-4(x+5)(x+5)=x^2-5x-5x+25-4(x^2+5x+5x+25)=x^2-5x-5x+25-4x^2-20x-20x-100=-3x^2-50x-75