3x^2-4xy-4y^2-6x-4y=(3x+2y)(x-2y)-2(3x+1y)=(3x+2y)(x-2y-2)
3x^2-4xy-4y^2-6x-4y =(3x+2y)(x-2y)-2(3x+1y) =(3x+2y)(x-2y-2)