在等差數(shù)列
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中,有
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,則此數(shù)列的前13項之和為
本題考查等差數(shù)列的性質(zhì)
由等差數(shù)列的性質(zhì)得
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,
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由
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得
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所以
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所以數(shù)列的前13項之和為
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故正確答案為C
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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
已知數(shù)列
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中,


,對于函數(shù)

有
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(1)證明數(shù)列

為等比數(shù)列,并求

的通項公式
(2)若
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,求和

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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
(本小題共14分)
數(shù)列
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的前n項和為

,點

在直線

上.
(I)求證:數(shù)列

是等差數(shù)列;
(II)若數(shù)列

滿足

,求數(shù)列

的前
n項和
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(III)設(shè)

,求證:

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(本小題滿分12分)已知數(shù)列

,
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
。
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
}的倒均數(shù)是
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,求數(shù)列{

}的通項公式

;
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的首項為-1,公比為
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
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
項之和
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
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),記第

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
,例如

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
的值;
小題2:求第
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
;
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來源:不詳
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
中,

,且

,

,

成等差數(shù)列.
(Ⅰ)求數(shù)列

的通項公式;
(Ⅱ)設(shè)數(shù)列

的前
n項和為

,求
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的最大值.
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
已知

是等差數(shù)列

的前

項和,若

,則

的值是( )
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