求y=x^3+2x^2+5x+6的零点是多少?

x^3+2x^2-5x-6=0
x^3+x^2+x^2-5x-6=0
x^2(x+1)+(x+1)(x-6)
(x+1)(x^2+x-6)
(x+1)(x+3)(x-2)=0
x=-1或x=-3或x=2