X的立方-2X+1=0
x^3-1+1-2x+1=0
(x-1)(x^2+x+1)-2(x-1)=0
(x-1)(x^2+x+1-2)=0
(x-1)(x^2+x-1)=0
x-1=0 或x^2+x-1=0
x=1 或x=(-1±√5)/2