x^3-3x+2=0
(x^3-x)-(2x-2)=0
x(x^2-1)-2(x-1)=0
x(x-1)(x+1)-2(x-1)=0
(x-1)(x^2+x-2)=0
(x-1)(x-1)(x+2)=0
(x-1)^2(x+2)=0
x-1=0或x+2=0
x=1或x=-2