(本小題滿分14分)已知數(shù)列
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是遞增數(shù)列,且滿足
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(Ⅰ)若
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是等差數(shù)列,求數(shù)列
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的通
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項公式;
(Ⅱ)對于(Ⅰ)中
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,令
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,求數(shù)列
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的前
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項和
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.
解:(1)根據(jù)題意:
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,又
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,
所以
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是方程
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的兩根,且
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,
解得
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,所以
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,
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. ……………………………6分
(2)
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,則
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①
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②
①一②,得
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,
所以
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. …………………………………………14分
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、
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、
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對
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