...满足 , ,数列 的前 项和为 .(1)求数列 的通项公式;(2)设
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发布时间:2024-02-13 15:52
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时间:2024-03-06 11:25
解:(1)由 得 代入 得
整理得 ,----------------------------------------------------------------1分
∵ 否则 ,与 矛盾
从而得 , ---------------------------------------------------------------------3分
∵ ∴数列 是首项为1,公差为1的等差数列
∴ ,即 .---------------------------------------------------------------4分
(2)∵
∴ =
= ---------------------------------------------------------6分
证法1:∵
= =
∴0 .--------------------------------------------------------------------------8分
证法2:∵ ∴
∴
∴0 .----------------------------------------------------------------------------8分
(3)用数学归纳法证明:
①当 时 ,不等式成立;-----------9分
②假设当 ( , )时,不等式成立,即
,那么当 时
----------------------------------------------------------------------12分
=
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