已知等差数列
的前
项和为
,且
,
.
(1)求
;
(2)若
+2 ,求
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.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/47dce0a1fe55239f8017915d53669ecb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b6a06993302797ce9ad5bc97381d3fd.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/99ffbaa47f3618fac94c1df652b7e6cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
21-22高三上·重庆沙坪坝·期中 查看更多[2]
更新时间:2021-11-27 12:27:01
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【推荐1】已知等差数列{an}满足:a4=7,a10=19,其前n项和为Sn.
(1)求数列{an}的通项公式an及Sn;
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fa172af12f6033165c5820b31566b4e.png)
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【推荐2】等差数列
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/089a641667b265ea147990144eddf2ba.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d5b91f98a46442f919b9db8ab0fd6c25.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/846fa57d92d6ad44d6a0cafad1e71ed4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
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【推荐3】定义首项为1且公比为正数的等比数列为“
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b9ac6bff34bf90d8f8b145315df55ce.png)
(1)已知等比数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef7017fe5e2318fd6a807e576db091ca.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce213373f9309f9bdb7ae4e094e31089.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b9ac6bff34bf90d8f8b145315df55ce.png)
(2)已知数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59dd6c97d2ee3e74ba5730f1cbcc1d43.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1b11b53600b5f8795438b5071251fe32.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b9ac6bff34bf90d8f8b145315df55ce.png)
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【推荐1】某公司2021年年初花费25万元引进一种新的设备,设备投入后每年的收益均为21万元.若2021年为第1年,且该公司第
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef65559a6b44930addc23adeb8d854c9.png)
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(2)引进这种设备后,第几年该公司开始获利?
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【推荐2】在等差数列{
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/daf464629fa321a6ff7401ab79f07083.png)
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【推荐1】设数列
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
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【推荐2】已知等差数列
的前
项和为
,且满足
,
.
(1)求数列
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(2)记
,求数列
的前
项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.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/668144ced4514790322b1d1421f5ed65.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8af92c06ea15668b9fe91c97fcc6a21.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)记
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e5f5061101ed3fc39e89d4c9097787f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
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