4(x^2+3x+1)^2-(x^2+x-4)-(x^2+5x+6)^2
=(2x^2+6x+2+x^2+5x+6)(2x^2+6x+2-x^2-5x-6)-(x^2+x-4)
=(3x^2+11x+8)(x^2+x-4)-(x^2+x-4)
=(3x^2+11x+7)(x^2+x-4)