cho 5 diem A B C D E sao cho 3 diem a b c thang hang ba diem b c d thang hang ba diem b c e khong thang hang a) giai thich vi sao ba diem a b d thang hang? b)ke duong thang moi duong thang di qua it nhat 5 diem tren c)ke ten cac duong thang trong hinh ve