Cho 21 diem.Qua 2 diem ve duoc 1 doan thang.Co tat ca bao nhieu doan thang?
Thay 21 diem boi n (n thuoc N,n lon hon hoac bang 2) so doan thang co duoc la bao nhieu?
Cho n diem (n thuoc N va n lon hon 1).Ve cac doan thang di qua cac cap diem duoc so doan thang nhieu hon 406 doan thang nhung it hon 465 doan thang .Tim n
Cho n diem cu noi 2 diem ta ve duoc mot doan thang.
a)Hoi co tat ca bao nhieu doan thang
b)Tim n biet so doan thang ve duoc la 55
cho n diem (n la so tu nhien lon hon1) cu 2 diem ta dc 1 doan thang. Hoi n bang bao nhieu de co so doan thang bang tong cac so tu nhien tu 1 den 99?
Cho truoc 10 diem trong do khong co 3 diem nao thang hang.
a) Hoi ve duoc bao nhieu duong thang?
b) Neu thay 10 diem bang n diem (n thuoc N, n > 2) thi ve duoc bao nhieu duong thang?
Cho n diem (n>hoac = 2)trong do co co 3 diem nao thang hang nua.Cu qua 2 diem ve 1 duong.Hoi ve duoc tat ca bao nhieu duong thang di qua 2 trong n diem do?
Cho 9 diem trong do khong co 3 diem nao thang hang . Cu di qua 2 diem la duoc mot doan thang.
Hoi co the ve duoc bao nhieu doan thang ?
minh khong biet viet dau nen cac ban thong cam !
Cho 5 diem A, B, C, D, E phan biet. Cu qua hai diem ta ve duoc 1 doan thang. Hoi co tat ca bao nhieu doan thang ?
trong mat phang cho 10 diem phan biet, trong do khong co 3 diem nao thang hang.Hoi co the ve duoc bao nhieu tia, bao nhieu doan thang, bao nhieu duong thang? (neu trong diem phan biet do co 5 diem thang hang thi ve duoc bao nhieu tia, bao mhieu doan thang, bao nhieu duong thang).