x³-2x²+1
=x³-x²-x²+x-x+1
=x²(x-1)-x(x-1)-(x-1)
=(x-1)(x²-x-1)=0
x-1=0或x²-x-1=0
x1=1
x2=(1+根号5）/2
x3=(1-根号5）/2