Question 289073
  x^3+3x^2-2x^2-6x=-2x^2-2x ok
  x^3+x2-6x=-2x^2-2x ok
  x^3+x^2+2x^2-6x=-2x^2+2x^2-2x ok but confusing
  x^3+3x^2-6x=-2x+2x  not ok
  x^3+3x^2-4x=0 ok
picking up 
x^3+x^2-6x=-2x^2-2x 
x^3+3x^2-4x=0
x*(x^2+3x-4)=0
x*(x+4)*(x-1)=0
x=0,1,-4