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 minh 5n+3/3n+2la phan so toi gian (n thuoc Z)
chung minh rang : Voi moi n thi phan so 7n+4/5n+3 la phan so toi gian .
chung to rang voi moi so nguyen n phan so 3n-5/3-2nla 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
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)
chung to p/s -3n+7/5n-12 luon toi gian voi moi so nguyen n
cach lam bai : chung to rang moi phan so co dang n+2015/n+2016 ( voi n thuoc N ) deu la phan so toi gian
