4x^2+4xy-3y^2+2x+11y-6 =(2x-y)(2x+3y)+2x+11y-6 =(2x-y)(2x+3y)+3(2x+3y)-4x+2y-6 =(2x+3y)(2x-y+3)-2(2x-y+3) =(2x-y+3)(2x+3y-2)