已知公差不為零的等差數(shù)列
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中,
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,且
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成等比數(shù)列.
(Ⅰ)求數(shù)列

的通項公式;
(Ⅱ)令
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(
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),求數(shù)列
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的前
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項和
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.
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科目:高中數(shù)學
來源:不詳
題型:解答題
各項均為正數(shù)的等差數(shù)列
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首項為1,且

成等比數(shù)列,

(1)求
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、
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通項公式;
(2)求數(shù)列

前n項和
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;
(3)若對任意正整數(shù)n都有
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成立,求
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范圍.
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科目:高中數(shù)學
來源:不詳
題型:填空題
已知等差數(shù)列

的首項

公差

,則當n=_________時,前n項和

取得最大值.
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科目:高中數(shù)學
來源:不詳
題型:解答題
已知公差不為零的等差數(shù)列

的前四項和為10,且

成等比數(shù)列
(1)求通項公式

(2)設

,求數(shù)列
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的前
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項和
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科目:高中數(shù)學
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已知數(shù)列

的前項和為
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,滿足

,
(1)令
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,證明:
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;
(2)求數(shù)列

的通項公式。
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科目:高中數(shù)學
來源:不詳
題型:解答題
數(shù)列{a
n}是公比為
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的等比數(shù)列,且1-a
2是a
1與1+a
3的等比中項,前n項和為S
n;數(shù)列{b
n}是等差數(shù)列,b
1=8,其前n項和T
n滿足T
n=n
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·b
n+1(
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為常數(shù),且
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≠1).
(I)求數(shù)列{a
n}的通項公式及
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的值;
(Ⅱ)比較
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+
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+

+ +
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與了
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S
n的大�。�
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科目:高中數(shù)學
來源:不詳
題型:單選題
已知數(shù)列
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是等差數(shù)列
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,
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,
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的前
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項和為
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,則使得
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達到最大的
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是( )
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科目:高中數(shù)學
來源:不詳
題型:單選題
在等差數(shù)列
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中,
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,則數(shù)列
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前
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項和
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取最大值時,
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的值等于( )
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科目:高中數(shù)學
來源:不詳
題型:填空題
一同學在電腦中打出如下若干個圈:○●○○●○○○●○○○○●○○○○○●…若將此若干個圈依此規(guī)律繼續(xù)下去,得到一系列的圈,那么在前120個圈中的●的個數(shù)是 。
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