bai 1;cho 4 diem A,B,C,D.  trong do khong co 3 diem nao thang hang. hoi co bao nhieu tam giac ma co 3 dinh la 3 trong 4 diem tren.

bai 2;   cung hoi nhu bai 1, voi 10 diem A1,A2,A3,............A10

                 GIUP TO VOI

cho doan thang AB=1m .lau A1 la trung diem cua doan thang AB,A2 la trung diem cua AA1,A3 la trung diem cua AA2.... cu tiep tuc nhu vay cho den A20 la trung diem cua AA19.tinh AA1+AA2+AA3+............+AA20

cho doan thang AB=1m .lau A1 la trung diem cua doan thang AB,A2 la trung diem cua AA1,A3 la trung diem cua AA2.... cu tiep tuc nhu vay cho den A20 la trung diem cua AA19.tinh AA1+AA2+AA3+............+AA20

cho 100 doan thang A1 ,A2 ,A3 ....... ,A100trong do khong co ba diem nao thang hang .Goi S la tong cac doan thang nhan 2 diem trong cac diem do lam dau mut . So sanh Sva 5000

tren doan thang AB lay 2006 diem khac nhau dat ten tu A den B la A1;A2;A3....A2004.tu diem M ko nam tren doan thang AB ta noi M voi cac diem A1;A2;A3;....A2004;B. tinh so tam giac tao thanh

Tren duong thang d lay theo thu tu cac diem A1, A2, A3... A2000 va 1 diem B nam ngoai duong thang d. Co bao nhieu tam giac ma 3 dinh la cac diem noi B voi A1, A2, A3... A2000         ( giup voi, sao hong ai giup tui vay, help)

cho n diem A1,A2,A3,....An( n>hoac =2) trong do ko co 3diem thang hang nao. cu 2 diem ke mot duong thang .

a) Ke ten cac duong thang neu n=4

b) tinh so duong thang tren hinh ve neu n=42

c) Tinh n biet so duong thang la 630

Tren duong thang xy lay 10 diem A1, A2, A3, A4...A10. Hoi co bao nhieu diem phan biet trong hinh ve.

Giai ro ra gium minh voi.

trong mat phang lay 2016 diem nao do A1,A2,A3,...,A2016. nguoi ta to tat ca cac trung diem cua cac doan thang noi cac cap diem trong so 2016 diem nay. goi T la so cac diem duoc to do . Tim gia tri lon nhat , gia tri nho nhat cua T

Cac ban giup minh nhe