Re: 94東吳資管
1 ∞ n
--- = Σ x
1-x n=0
x ∞ n-1+1
----- = Σ nx
(1-x)^2 n=1
所以 原式=(1/2)/(1/2)^2 =2
大學生要有大學生的做法
老師改到會喜歡你這樣寫的
※ 引述《dichia (回憶的牽絆)》之銘言:
: 今天有一題
: Find the sum of the series
: ∞ n
: Σ ---
: n=1 2^n
: 我只用ratio test證明到他收斂 後面就不會了....
: 還是根本用不到ratio test啊....?
: 麻煩解答了...謝謝
--
※ 發信站: 批踢踢實業坊(ptt.cc)
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