x−2y−6=0x-2 y-6=0x−2y−6=0
x+2y−6=0x+2 y-6=0x+2y−6=0
x+2y+6=0x+2 y+6=0x+2y+6=0
x−2y+6=0x-2 y+6=0x−2y+6=0
