x^3-3x+2=0
(x^3-4x)+(x+2)=0
x(x^2-4)+(x+2)=0
x(x+2)(x-2)+(x+2)=0
(x+2)[x(x-2)+1]=0
(x+2)(x^2-2x+1)=0
(x+2)(x-1)^2=0
x=-2或x=1