(12分)设函数
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为奇函数,且
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,数列
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与
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满足如下关系:
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(1)求
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的解析式;(2)求数列
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的通项公式
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;(3)记
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为数列
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的前
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项和,求证:对任意的
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有
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(Ⅰ)
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(Ⅱ)
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(Ⅲ)略
:(1)由
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是奇函数,得
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,由
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,得
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故
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(2)∵
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∴
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∴
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,而
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,∴
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(3)证明:由(2)
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要证明的问题即为
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当
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时,
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当
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时,
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∴
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则
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故
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则
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得证
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的前
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,
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,

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).
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为其前
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项的和,且
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(I)分别求
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,
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的值;(II)求数列

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已知等差数列
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
成等比数列.
(Ⅰ)求数列
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的通项公式;
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中依次取出第2项、第4项、第8项,……,

,……,按原来顺序组成一个新数列

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项和为
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,求
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已知
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为数列
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的前
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项和,
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,
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.
⑴求数列
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的通项公式;
⑵数列
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中是否存在正整数
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,使得不等式
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对任意不小于
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的正整数都成立?若存在,求最小的正整数
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,若不存在,说明理由.
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