已知等差数列{an}满足a1=3,当n≥2时an﹣1+an=4n.
(1)求数列{an}的通项公式;
(2)若数列{bn}满足
,求数列{bn}的前n项和Sn.
(1)求数列{an}的通项公式;
(2)若数列{bn}满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf1b3d5c520b26fbf843bdc9479a3072.png)
20-21高二·全国·单元测试 查看更多[2]
更新时间:2020-09-09 11:04:32
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解答题-问答题
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【推荐1】下表是一个“数阵”:
其中每行都是公差不为0等差数列,每列都是等比数列,
表示位于第i行第j列的数.
(1)写出
的值:
(2)写出
的计算公式,以及第2020个1所在“数阵”中所在的位置.
1 | ( ) | ( ) | ( ) | … | ![]() | … |
( ) | 1 | ( ) | ( ) | … | ![]() | … |
( ) | ( ) | ( ) | 1 | … | ![]() | … |
… | … | … | … | … | … | … |
![]() | ![]() | ![]() | ![]() | … | ![]() | … |
… | … | … | … | … | … | … |
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/37a14c188b1c9d61aa237b137ba18023.png)
(1)写出
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/978ffc56dc86a126e896378c79f6a841.png)
(2)写出
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/37a14c188b1c9d61aa237b137ba18023.png)
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【推荐2】在①
,
;②
,
;③
,
三个条件中任选一个,补充在下面问题中,并解答.
已知等差数列
的公差为
,前
项和为
,等比数列
的公比为
,且
,
,___________;求数列
、
的通项公式.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8a0eecb5b800fce9ae10aed86ffee62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2af89f6a66ba3f325fc395902848ef58.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73e96fafcc7b7f783d436f853449208d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cc53f39107ae6154b3745794f3c0780.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5170584604571b5e1afd5ece941e2e73.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/735d27e28a42909284a7b02d633f1ac2.png)
已知等差数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/251299e21f8b20cacaa0a4a851376b97.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/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9aa8a716a31b0f51b70fdf9bdb257909.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89fe0f4e8a80a2840c0f6929a8a6351b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5518372eecda4c1ea288113b7ff4702b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
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【推荐3】在下面的数表中,各行中的数从左到右依次成公差为正数的等差数列,各列中的数从上到下依次成公比为正数的等比数列,且公比都相等,
表示第
行,第
列的数.已知
.
(1)求数列
的通项公式;
(2)设
,求数列
的前n项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b369b8ba12b922f685162a2088a03ec.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4030e92fb94add3eff0ed4c1843f560.png)
第一列 | 第二列 | 第三列 | 第四列 | … | |
第一行 | a(1,1) | a(1,2) | a(1,3) | a(1,4) | … |
第二行 | a(2,1) | a(2,2) | a(2,3) | a(2,4) | … |
第三行 | a(3,1) | a(3,2) | a(3,3) | a(3,4) | … |
第四行 | a(4,1) | a(4,2) | a(4,3) | a(4,4) | … |
… | … | … | … | … | … |
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/980cddae9384f928da5a790c6a983471.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6de894fd503267b5b62bb5716d21459e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5ab0309e2cd35585ea9fb2cc3017abf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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解答题-问答题
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适中
(0.65)
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解题方法
【推荐1】
是数列
的前n项和,根据条件求
.
(1)
;
(2)
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
(1)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/98f38edcccff7ddc9e9a77c49d2216e4.png)
(2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fc5eac09ed870c6711d94e558a25a9b.png)
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解答题-问答题
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适中
(0.65)
解题方法
【推荐2】已知数列
的前n项和是
,且
.求:
(1)数列
的通项公式;
(2)数列
落入区间
内的所有项的和.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3c07d6d0c63061e09e36b5a2c74760b.png)
(1)数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/07cca47bffd3489226a44c88d2052c04.png)
您最近一年使用:0次
【推荐1】已知数列{an}的前n项和为Sn,且满足Sn=2an﹣2n﹣1,(n∈N+).
(Ⅰ)求证:数列{an+2}是等比数列;
(Ⅱ)求数列{n•(an+2)}的前n项和.
(Ⅰ)求证:数列{an+2}是等比数列;
(Ⅱ)求数列{n•(an+2)}的前n项和.
您最近一年使用:0次
【推荐2】已知正项数列
满足:
,
,
.
(1)证明:
是等差数列并求数列
的通项公式;
(2)设
,求数列
的前
项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5be425167c4cf003028d17267a0eade2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/14835bf3f00139ccec0694d0924db795.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b012a5b5d4456f86eed09c698b9c07f3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cea4ac187cbb465180e89f38250b3970.png)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/17c1cb5ecde6b0431f255112cf1c8668.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5be425167c4cf003028d17267a0eade2.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f052af7ec6eabf99cbea5543397cd1d5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/43b7e7cd571c8cd141cbbfe5d0890bf6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
您最近一年使用:0次