9x^4 - 3x^3 + 7x^2 - 3x + 2
=9x^4+3x^3+6x^2-6x^3-2x^2-4x+3x^2+x+2
=3x^2(3x^2+x+2)-2x(3x^2+x+2)+(3x^2+x+2)
=(3x^2+x+2)(3x^2-2x+1)