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chung minh rang : Voi moi n thi phan so 7n+4/5n+3 la phan so toi gian .
CMR: Neu phan so 7n^2+1/6 la so tu nhien voi n thuoc N thi cac phan so n/2 va n/3 la cac phan so toi gian
chung minh: Voi moi n thi phan so 7n+4/5n+3la phan so toi gian
Chung minh rang moi phan so dang n+1/2n+3 ( n thuoc N ) deu la phan so toi gian.
chung minh 5n+3/3n+2la phan so toi gian (n thuoc Z)
Chung minh rang phan so sau toi gian voi moi n thuoc N 2n+1/2n(n+1)
cho phan so p=6n+5/3n+2 (n thuoc N)
chung minh rang phan so p la phan so toi gian
giup minh nhe
1) Biet rang 996 va 632 khi chia cho n deu du 16 . Tim n.
2) Chung minh rang 7n + 10 va 5n + 7 la hai so nguyen to cung nhau ( n thuoc N )
3) Biet rang 7a + 2b chia het cho 13 (a,b thuoc N) . Chung minh rang 10a + b cung chia het cho 13
Cho n thuoc N, chung to cac phan so sau la toi gian :
a, 2n+1/5n+2
b, 5n+2/3n+1
c, 5n+2/(3n+1).(2n+1)