試題分析:∵
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,∴
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,
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,
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,
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,
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,…,故數(shù)列
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的周期為3,∴
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,故選B
點評:通過觀察找出所給數(shù)列的周期性,然后求解數(shù)列的項,是解決此類問題的關鍵
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、

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
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
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
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
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
,則雙曲線

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
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
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
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
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
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
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
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
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
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
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
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
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
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
的前

項和

.
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
:

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
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(2)若

,設

,求
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。
(3)設
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,

為數(shù)列

的前

項和,求
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(1)已知數(shù)列

的前

項和為

,

,

,求
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(2)已知等差數(shù)列

的前
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項和為

,求數(shù)列
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的前2012項和
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