數型問題．都幾深^^

General Term : 3^(n - 1)
Second term / First term = 3/1 = 3 = r
Third Term / Second Term = 9/3 = 3 = r
First Term = 1 = a
By the formula a * r^ (n- 1)
i.e. 3^(n - 1)


2008-08-22 15:46:38 補充：
若果是 ?n 就諗唔到,
但係呢個一定岩....