在等差數(shù)列3, 7, 11 …中,第5項為( )
試題分析:由題意知
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,
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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
已知數(shù)列
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滿足:
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且
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.
(1)求數(shù)列
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的通項公式;
(2)令
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,數(shù)列
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的前項和為
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,求證:
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時,
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且
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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
已知
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為公差不為零的等差數(shù)列,首項
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,
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的部分項
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、
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、…、
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恰為等比數(shù)列,且
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,
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,
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.
(1)求數(shù)列
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的通項公式
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(用
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表示);
(2)若數(shù)列
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的前
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項和為
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,求
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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
設(shè)不等式組
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所表示的平面區(qū)域為
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,記
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內(nèi)的格點(格點即橫坐標和縱坐標均為整數(shù)的點)個數(shù)為
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(1)求
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的值及
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的表達式;
(2)設(shè)
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為數(shù)列
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的前
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項的和,其中
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,問是否存在正整數(shù)
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,使
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成立?若存在,求出正整數(shù)
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;若不存在,說明理由
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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
數(shù)列
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是等差數(shù)列,
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,前四項和
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。
(1)求數(shù)列
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的通項公式;
(2)記
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,計算
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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
[2013·大連模擬]已知數(shù)列{a
n}的前n項和S
n=n
2-6n,則{|a
n|}的前n項和T
n=( )
A.6n-n2 |
B.n2-6n+18 |
C. |
D. |
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
[2014·天津市模擬]若等差數(shù)列{a
n}的前5項和S
5=25,且a
2=3,則a
7=( )
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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
(2013•重慶)設(shè)數(shù)列{an}滿足:a1=1,an+1=3an,n∈N+.
(1)求{an}的通項公式及前n項和Sn;
(2)已知{bn}是等差數(shù)列,Tn為前n項和,且b1=a2,b3=a1+a2+a3,求T20.
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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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為等差數(shù)列
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的前
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項和,若
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,公差
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,
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,則
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( )
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