x²-4xy+3y²-4x+10y+3
=(x-y)(x-3y)-4x+10y+3
=(x-y-3)(x-3y-1)
x²+xy-2y²+2x+7x-3
=(x+2y)(x-y)+2x+7y-3
=(x+2y-1)(x-y+3)