1 . 我们把公差不为0的等差数列
称为“一阶等差数列”,若数列
是“一阶等差数列”,则称数列
是“二阶等差数列”.定义:若数列
是“
阶等差数列”,则称数列
为“
阶等差数列”.例如:
,后项与前项的差值:
,这些差值构成的数列是公差为2的等差数列,则称数列
为“二阶等差数列”.
(1)若数列
的通项公式为
,试判断数列
是否为“二阶等差数列”,并说明理由;
(2)若数列
为“二阶等差数列”,且
,对应的“一阶等差数列”首项为1,公差为3,求
;
(3)若“三阶等差数列”
的前4项依次为
,其前
项和为
,求
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11f2bee5c248cf87d219a507455e1083.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d82c65a855b1eed9c43e6829f6c3bffb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76aef4cdcb5af742ce28003b7b6c8c20.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d82c65a855b1eed9c43e6829f6c3bffb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76aef4cdcb5af742ce28003b7b6c8c20.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1b00f4eb7f1bd2ccefbabf0c1dfa8f69.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7e4f8df1315b49f394a562293f6b9cd9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42090ea706a016125ab40d40bf17004b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7e4f8df1315b49f394a562293f6b9cd9.png)
(1)若数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76aef4cdcb5af742ce28003b7b6c8c20.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0dd3ce757a2ad080ece0e34424fb05f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76aef4cdcb5af742ce28003b7b6c8c20.png)
(2)若数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76aef4cdcb5af742ce28003b7b6c8c20.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
(3)若“三阶等差数列”
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76aef4cdcb5af742ce28003b7b6c8c20.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb3a7a91f234f673e5686b0692d109e7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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2 . 已知数列
是等差数列,且
,数列
满足
,
,且
.
(1)求数列
的通项公式;
(2)将数列
的所有公共项按从小到大的顺序组成一个新的数列
,求数列
的通项公式;
(3)设数列
的前
项和为
,证明:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/562bf10d55724c77204c6953c7fbf7e2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7d209e2de5018771d56c876e8aa5852c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a42ad99786dd67c784e880b5744e623.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/470aabd74beb1f61cf4f4622372d3b48.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
(2)将数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/62e567d7e9761951a266953c8d5042ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57ef6d44448092ebdb9e4a49d866a749.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57ef6d44448092ebdb9e4a49d866a749.png)
(3)设数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2375ec49c4e7fee0753a6121c800cae3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e0d96f66526ecb7b8546604e2c45c40.png)
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3 . 如图,用相同的球堆成若干堆“正三棱锥”形的装饰品,其中第1堆只有1层,且只有1个球;第2堆有2层4个球,其中第1层有1个球,第2层有3个球;…;第n堆有n层共
个球,第1层有1个球,第2层有3个球,第3层有6个球,….已知
,则
( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d0404fc0e1e978897ab93fab55968444.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c999598630489185102e09472ffbb151.png)
A.2290 | B.2540 | C.2650 | D.2870 |
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4 . 已知数列
满足:
,
,
.
(1)证明:
是等差数列,并求
的通项公式;
(2)设
,若数列
是递增数列,求实数
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/18d8e8f821111de8075e5c3dfb22a5d6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3938fc9093a10b040b5ed9d18c876637.png)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d82c65a855b1eed9c43e6829f6c3bffb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce522f63743302ecdffabd13df6f8526.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
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5 . 已知数列
满足
,数列
为公差为
的等差数列,且满足
.记
,称
为由数列
生成的“
函数”.
(1)求
的值;
(2)若“1-函数”
,求n的最小值;
(3)记函数
,其导函数为
,证明:“
函数”
.
附:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8323901a49cac29afd7d62864f088077.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bf5de3a713c5fec698c5744651ae1bd4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5653b60d16ec4e653518f0562680250.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d21cd719d0bc42c0b0374eeb37096d87.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e058f4325169eafcc30081eaf45327a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb654dbe976f077495105b21b7963d0f.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c3e848bb6f5f46e05b18cf98389f5cd9.png)
(2)若“1-函数”
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fc1c9ff5089917a26e631e3f3232df0.png)
(3)记函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4d80dabbd911f2ce3d28b57631aa143.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/16d2609c74aa40ca949104053aca2651.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb654dbe976f077495105b21b7963d0f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a899b8b209c4e7b4ee15473a9c945270.png)
附:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f3d03cc0ef5d26ba82c79edd397fbe34.png)
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名校
解题方法
6 . 已知数列
满足
,则( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e248d051061499434839cc091ba202c.png)
A.![]() |
B.![]() |
C.![]() |
D.当![]() ![]() |
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7 . 已知函数
,数列
满足
正整数
(1)求
的最大值;
(2)求证:
;
(3)求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/374f4dc3c1593925bcffe29045d50ae6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76aef4cdcb5af742ce28003b7b6c8c20.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d75a73fe7c160831df3f3f1acc0ba10e.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fe7d5809da02c15a43a0e9a898b9086.png)
(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b92028ad968685f0e9db216980d5093a.png)
(3)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b55e3ad996ee541b01f14d2c99d32f3.png)
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解题方法
8 . 已知数列
满足
,则( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42349f927ff9adb340a57fdc5cc69ae9.png)
A.![]() | B.数列![]() |
C.![]() | D.数列![]() ![]() |
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9 . 如图的形状出现在南宋数学家扬辉所著的《详解九章算法·商功》中后人称为“三角垛”,“三角垛”最上层有1个球,第二层有3个球,第三层有6个球,…,设第n层有
个球,从上往下n层球的总数为
,则说法不正确的是( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
A.![]() | B.![]() |
C.![]() | D.不存在正整数![]() ![]() |
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