x³-2x²+1=x³-x²-x²+1=x²(x-1)-(x+1)(x-1)=(x²-x-1)(x-1)
x³-2x²+1=x³-x²-x²+1=x²(x-1)-(x²-1)=(x-1)[x²-(x+1)]=(x-1)(x²-x-1)=(x-1)(x-(1+√5)/2)(x-(1-√5)/2)
(x-1)外的平方
