x^3+6x^2+11x+6=0
(x^3+6x^2+9x)+(2x+6)=0
x(x^2+6x+9)+2(x+3)=0
x(x+3)^2+2(x+3)=0
(x+3)[x(x+3)+2]=0
(x+3)(x+2)(x+1)=0
x+3=0 x1=-3
x+2=0 x2=-2
x+1=0 x3=-1