已知

是等差數(shù)列

的前

項和,且
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,則

等于( )
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科目:高中數(shù)學
來源:不詳
題型:解答題
已知

為等比數(shù)列,

是等差數(shù)列,

(Ⅰ)求數(shù)列

的通項公式及前

項和

;
(2)設


,


,其中

,試比較

與

的大小,并加以證明.
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科目:高中數(shù)學
來源:不詳
題型:解答題
設數(shù)列

的前n項和為

,已知

,

,數(shù)列

是公差為d的等差數(shù)列,

.
(1)求d的值;
(2)求數(shù)列

的通項公式;
(3)求證:

.
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科目:高中數(shù)學
來源:不詳
題型:解答題
已知等差數(shù)列

的前n項和為

,且

,

.
(Ⅰ)求數(shù)列

的通項

;
(Ⅱ)設

,求數(shù)列

的前n項和

.
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科目:高中數(shù)學
來源:不詳
題型:解答題
已知

是正數(shù)組成的數(shù)列,

,且點

在函數(shù)

的圖象上.
(Ⅰ)求數(shù)列

的通項公式;
(Ⅱ)若數(shù)列

滿足

,

,求證:


.
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科目:高中數(shù)學
來源:不詳
題型:解答題
設等比數(shù)列

的首項為

,公比為

(

為正整數(shù)),且滿足

是

與

的等差中項;數(shù)列

滿足

(

).
(Ⅰ)求數(shù)列

的通項公式;
(Ⅱ)試確定

的值,使得數(shù)列

為等差數(shù)列;
(Ⅲ)當

為等差數(shù)列時,對每個正整數(shù)

,在

與

之間插入

個2,得到一個新數(shù)列

. 設

是數(shù)列

的前

項和,試求滿足

的所有正整數(shù)

.
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科目:高中數(shù)學
來源:不詳
題型:解答題
數(shù)列

前

項和

,數(shù)列

滿足

(

),
(1)求數(shù)列

的通項公式;
(2)求證:當

時,數(shù)列

為等比數(shù)列;
(3)在題(2)的條件下,設數(shù)列

的前

項和為

,若數(shù)列

中只有

最小,求

的取值范圍.
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科目:高中數(shù)學
來源:不詳
題型:單選題
等差數(shù)列

的前n項和為

,且滿足

,則下列數(shù)中恒為常數(shù)的是( �。�
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科目:高中數(shù)學
來源:不詳
題型:單選題
設

為等差數(shù)列,且

,則數(shù)列

的前13項的和為

( )
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