等差數(shù)列
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的前n項(xiàng)和為
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,若
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,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:解答題
(14分)已知數(shù)列{an}的前n項(xiàng)和為Sn,且an是Sn與2的等差中項(xiàng),數(shù)列{bn}中,b1=1,點(diǎn)P(bn,bn+1)在直線x-y+2=0上。 (1)求a1和a2的值; (2)求數(shù)列{an},{bn}的通項(xiàng)an和bn; (3)設(shè)cn=an·bn,求數(shù)列{cn}的前n項(xiàng)和Tn。
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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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是首項(xiàng)
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公比
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的等比數(shù)列,設(shè)數(shù)列
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的通
項(xiàng)
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,數(shù)列
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、
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的前
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項(xiàng)和分別為
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.如果
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對
一切自然數(shù)
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都成立,求實(shí)數(shù)
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的取值范圍.
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
設(shè)
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是等差數(shù)列
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的前
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項(xiàng)和,
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,則
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的值為
A. | B.1 | C.2 | D.3 |
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
數(shù)列{a
n},a
1=
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,a
n=2-
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(n≥2)則a
2008等于 ( )
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
已知等差數(shù)列
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中,
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,則首項(xiàng)
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和公差
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的值分別為
A.1 ,3 | B.-3, 4 | C.1, 4 | D.1, 2 |
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
若1,
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,3成等差數(shù)列,1,
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,4成等比數(shù)列,則
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的值為( )
A.± | B.±1 | C.1 | D. |
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科目:高中數(shù)學(xué)
來源:不詳
題型:填空題
若數(shù)列
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中,
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,
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,則其通項(xiàng)公式
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=
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