x^4- 2x^3+2x-1=(x^4-1)- (2x^3-2x)=(x^2+1)(x^2-1)-2x(x^2-1)=(x^2-1)(x^2+1-2x)=(x^2-1)(x-1)^2=(x-1)(x+1)(x-1)(x-1)
=(х^4-1)-2х(х^2-1)=(х^2-1)(х^2+1)-2х(х^2-1)=(х^2-1)(х^2+1-2х)=(х-1)(х+1)(х-1)^2
