Re: [考古] 級數
※ 引述《power1106 (隱藏模式)》之銘言:
: n
: ∞ 2
: Σ -------- 收斂或發散?
: n=1 n+1
: 2 +1
∞ 1
= Σ -------------- because lim an = 1/2(不等於0) so~ diverge!
n=1 2 + 1 n→∞
----
2^n
: ∞ n
: Σ ---------------=? 不知如何下手!!
: n=1 (n+1)(n+2)(n+3)
: p.s.數學符號真難打= =a
∞ n 1 1
= Σ --- ( ------------- - ----------- )
n=1 2 (n+1)(n+2) (n+2)(n+3)
1 ∞ 1
= --- Σ ------------
2 n=1 (n+1)(n+2)
1 ∞ 1 1
= --- Σ ------- - -------
2 n=1 (n+1) (n+2)
= 1/2 * 1/2
= 1/4
極不負責任解答 極有可能兩題都寫錯 請自行驗算.........@@
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