Re: [中學] 無窮級數
※ 引述《susiseptem (..)》之銘言：
: 無窮級數 1 至 無窮大 n(1/3)^n 之值
: 感謝板上專業的大大QQ
: 100P答謝
S = Σn*(1/3)^n = 1*(1/3)+2*(1/3)^2+3*(1/3)^3+4*(1/3)^4+.....
(1/3)S = Σn*(1/3)^(n+1) = 1*(1/3)^2+2*(1/3)^3+3*(1/3)^4+4*(1/3)^5+...
(2/3)S = = 1*(1/3)+ (1/3)^2+ (1/3)^3+ (1/3)^4+.....
= (1/3)/[1-(1/3)]
= 1/2
S = 3/4
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05/15 23:52, , 1F
05/15 23:52, 1F
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