(x ^ 2-2x) ^ 2 + 2 (x ^ 2-2x) + 1 = factorization process

(x ^ 2-2x) ^ 2 + 2 (x ^ 2-2x) + 1 = factorization process

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