B
bacnammn


moi nguoi cho em hoi. trong de luyen/giai thi thu vat ly cua thay Hung. de so 16, cau 13. de yeu cau tinh so vi tri van trung tren doan MN, thay tinh n=2. vay thi se co 3 van trung tren MN ma sao lai co 2 vi tri van trung? em khong hieu lam. mong moi nguoi giup em.