X^3-2x^2+x=0 x^2-4x+4=0 x^4-8x^2+16=0
X(x^2-2x+1)=0 x=0 (x-1)^1=0 x=1 (x-2)^2=0 x-2=0 x=2 (x^2-4)^2=0 x^2=4 x=+-2