在实数域： x^4+1=x^4+2x^2+1-2x^2=(x^2+1)^2-2x^2=(x^2+√2x+1)(x^2-√2x+1)在复数域： x^4+1=(x+√2/2+i√2/2)(x+√2/2-i√2/2)(x-√2/2+i√2/2)(x-√2/2-i√2/2)
x^4+1=(x^2+i)(x^2-i)=[x-(1-i)/2]×[x+(1-i)/2]×[x-(1+i)/2]×[x-(1+i)/2]
