(數論)數學問題,求教please!!!!!!:(((((

Let gcd(a,b) = d , then a = dA , b = dB were (A,B) = 1. The sequence a , 2a , 3a ,..., ab becomes dA , 2dA, 3dA , .... , dBdA.The multiples of b = Bd in the sequence are
BdA , 2BdA , 3BdA , .... , (d-1)BdA , dBdA respectively.Total d terms , the result follow.

2013-04-13 14:18:11 補充：
每項都有因數A, 所以BdA是sequence中最小能被Bd整除的一項。

THX!!!!!!!!!!!!