x+2y−7=0x+2 y-7=0x+2y−7=0
x−2y−7=0x-2 y-7=0x−2y−7=0
x+2y+7=0x+2 y+7=0x+2y+7=0
x−2y+7=0x-2 y+7=0x−2y+7=0