設(shè)等差數(shù)列
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的公差
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≠0,
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.若
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是
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與
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的等比中項,則
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( )
試題分析:因
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是
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與
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的等比中項,所以
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,即
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,又
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,
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,則有
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,即
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(舍去).
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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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的前n項和為
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且
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,數(shù)列
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滿足
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且
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.
(1)求
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的通項公式;
(2)求證:數(shù)列
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為等比數(shù)列;
(3)求
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前n項和.
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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
設(shè)
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是數(shù)列
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的前
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項和,
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,
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,
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.
(1)求證:數(shù)列
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是等差數(shù)列,并
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的通項;
(2)設(shè)
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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(xué)
來源:不詳
題型:解答題
已知正項數(shù)列
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的首項
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,前
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項和
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滿足
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.
(Ⅰ)求證:
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為等差數(shù)列,并求數(shù)列
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的通項公式;
(Ⅱ)記數(shù)列
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的前
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項和為
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,若對任意的
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,不等式
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恒成立,求實數(shù)
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的取值范圍.
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來源:不詳
題型:單選題
已知
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、
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均為等差數(shù)列,其前
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項和分別為
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和
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,若
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,則
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值是( )
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
已知等比數(shù)列{
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}中,各項都是正數(shù),且
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成等差數(shù)列,則
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=( )
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
已知數(shù)列
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,
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,若該數(shù)列是遞減數(shù)列,則實數(shù)
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的取值范圍是( )
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
已知數(shù)列{
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}是公差為3的等差數(shù)列,且
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成等比數(shù)列,則
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等于( )
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
已知
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為等差數(shù)列,其前
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項和為
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,若
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,
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,則公差
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等于( )
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