Chung minh rang trong 3 so nguyen to lon hon 3 luon co 2 so nguyen to ma tong hoac hieu cua chung chia het cho 12
cho 4 so nguyen to lon hon 5.chung to rang luon ton tai it nhat hai so co tong hoac hieu chia het cho 18
chung minh rang trong ba so nguyen to lon hon 3 bao gio cung co 2 so ma tong hoac hieu chia et cho 12
CMR
neu p va p+2 la 2 so nguyen to lon hon 3 thi tong cua chung chia het cho 12
cho6 so tu nhien khac nhau co tong la 50.chung minh rang trong 6 so tu nhien da cho ton tai 3 so co tong lon hon hoac bang 30
chung minh rang trong 27 so tu nhien tuy y luon ton tai 2 so tu nhien co tong hoac hieu chia het cho 50
Chung minh rang p+2 va p+4 la so nguyen to lon hon 3 thi tong cua chung chia het cho 12.
chung minh rang trong 2 so nguyen duong bat ki luon tim duoc 2 so sao cho tong hoac hieu cua chung chia het cho 25
Cho day so sau : 1, 2, 3, ..., 200 ( 200 so ). Chon n so ( n lon hon hoac bang 2 ) sao cho co 2 so bat ki trong n so do sao cho tong cua 2 trong n so bat ki do chia het cho 2 voi n lon nhat.