已知多项式x^3+5x^2-4x-20 ,有一个因式是x+2,求其余的因式

x^3+5x^2-4x-20
=(x^3+4x^2+4x)+x^2-8x-20
=x(x^2+4x+4)+(x^2+4x+4)-12x-24
=x(x+2)^2+(x+2)^2-12(x+2)
=(x+2)[x(x+2)+(x+2)-12]
=(x+2)(x^2+2x+x+2-12)
=(x+2)(x^2+3x-10)
=(x+2)(x-2)(x+5)
还有两个因式为x-2和x+5