一元三次方程x^3+a1x^2+a2x+a3=0求根公式(又称卡丹公式),公式为:设p=-(a1^2/3)+a2,q=2a^3/27-a1a2/3+a3有
x1=[-q/2-(q^2/4+p^3/27)^(1/2)]^(1/3)+[-q/2+(q^2/4+p^3/27)^(1/2)]^(1/3)=u+v
x2=-1/2(u+v)+i/3^(1/2)*(u-v)
x3=-1/2(u+v)-i/3^(1/2)*(u-v)
所以结果为(x-x1)(x-x2)(x-x3)