數(shù)列
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中,
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,
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,
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,則該數(shù)列的通項為
。
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試題分析:根據(jù)題意,由于數(shù)列給定了遞推關(guān)系可知,數(shù)列
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中,
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,
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,
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,由此可知
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的等差中項,因此可知數(shù)列
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是等差數(shù)列,首項為1,公差為
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,因此可知其通項公式為
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,故答案為
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點評:解決的關(guān)鍵是能通過前幾項能發(fā)現(xiàn)其規(guī)律,得到數(shù)列的通項公式。屬于基礎(chǔ)題。
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項和
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有最大值,則使
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(Ⅰ)若
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,
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(Ⅰ)求證:數(shù)列
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