chung to rang voi moi so nguyen n phan so 3n-5/3-2nla phan so toi gian
chung to rang voi moi so tu nhien N gia tri cua 2 bieu thuc 7n+10 va 5n+7 luon la 2 so nguyen to cung nhau
CMR phan so 3n+2/5n+3 toi gian voi moi n thuoc N
Chung minh rang voi moi so n thi 2 so sau nguyen to cung nhau
2n+5 va 2n+7
2n+5 va 3n+8
5n+7 va 2n+3
chung minh: Voi moi n thi phan so 7n+4/5n+3la phan so toi gian
chung minh rang : Voi moi n thi phan so 7n+4/5n+3 la phan so toi gian .
cho A = 3N+2/6N+3
A TIM N DE a LA PHAN SO
b chung to A la phan so toi gian voi moi n thuoc N
Chung to rang voi moi so tu nhien n thi hai so 3n+5 va 5n+8 la hai so nguyen to cung nhau .
Chung minh cac phan so sau la phan so toi gian voi moi so nguyen n :A=12n+1 tren 30n+2
