f(x)=x^4-4x^3+4x^2-x^3+4x^2-4x+x^2-4x+4 =x^2(x^2-4x+4)-x(x^2-4x+4)+(x^2-4x+4) =(x^2-4x+4)(x^2-x+1) =(x-2)^2(x^2-x+1) 此为实数域的分解 若为复数域,则进一步有： f(x)=(x-2)^2[x-(1-i√3)/2][x-(1+i√3)/2]
