已知等差數(shù)列
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中,
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,則
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( )
A.30 | B.15 | C. | D. |
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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
(本題滿分16分)本題共有3個小題,第(1)小題滿分4分,第(2)小題滿分5
分,第(3)小題滿分7分.
將邊長分別為1、2、3、…、n、n+1、…(
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)的正方形疊放在一起,形成如圖所示的圖形,由小到大,依次記各陰影部分所在的圖形為第1個、第2個、……、第n個陰影部分圖形.設(shè)前n個陰影部分圖形的面積的平均值為
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.記數(shù)列
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滿足
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,
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(1)求
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的表達(dá)式;
(2)寫出
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的值,并求數(shù)列
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的通項公式;
(3)記
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,若不等式
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有解,求
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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:解答題
(本小題滿分12分)已知數(shù)列{
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}的前n項和為
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,數(shù)列
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的前n項和為
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,
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為等差數(shù)列且各項均為正數(shù),
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(1)求數(shù)列{
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}的通項公式;
(2)若
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成等比數(shù)列,求
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
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是數(shù)列
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的前
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項和,則“數(shù)列
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為常數(shù)列”是“數(shù)列
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為等差數(shù)列”的( )
A.充分不必要條件 | B.必要不充分條件 |
C.充分必要條件 | D.既不充分也不必要條件 |
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
在等差數(shù)列
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中,
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,則此數(shù)列的前
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項的和等于
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、
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、
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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:填空題
已知
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,
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,
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成等差數(shù)列,則①
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;②
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;③
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中,正確的是
.(填入序號)
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科目:高中數(shù)學(xué)
來源:不詳
題型:填空題
通項公式為
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的數(shù)列
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,若滿足
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,且
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對
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恒成立,則實數(shù)a的取值范圍是
▲
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科目:高中數(shù)學(xué)
來源:不詳
題型:填空題
在等差數(shù)列{an}中,a5+a10+a15+a20=20,則S24=
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科目:高中數(shù)學(xué)
來源:不詳
題型:填空題
已知
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為
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的內(nèi)角,且
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成等差數(shù)列,則角
;
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