maths~~~
回答 (1)
2009-11-03 7:46 am
✔ 最佳答案
Let the first term be a :The sum of the first 4 terms = a(1 - (2/3)^4) / (1 - 2/3) = 260/9
(65a/81) / (1/3) = 260/9
65a = 260*3
a = 12
The nth term
=12 (2/3)^(n-1)
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