解题方法
1 . 已知各项都是正数的等比数列
的前3项和为21,且
,数列
中,
,若
是等差数列,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80e714bab58ef7d55e9ea809d667e1df.png)
______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f0939caf47d751f8c7139bd0b25fe98.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/22f4af06d11d85f30ed9821682ef7a82.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5344eadd4711db34e3f935aedd5fb270.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80e714bab58ef7d55e9ea809d667e1df.png)
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解题方法
2 . 任意
,有
,若
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f48402431243ccf5e7e01edd64a0b8c3.png)
__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24a57996290794e082b21d8f1dfc322a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7368766dc6206018032c846a0b7ac91.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcc495172f6a0522ccd4f8d5122e6423.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f48402431243ccf5e7e01edd64a0b8c3.png)
您最近一年使用:0次
解题方法
3 . 已知公差为整数的等差数列
满足
,
,则
的前11项和为______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bde3113b24d3e16cc90612fb67865cfe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0ce62149b4bd48a9e52c5bce4e3317e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba57c83d526ac308d1461e80fcca9f36.png)
您最近一年使用:0次
名校
4 . 在等差数列
中,Sn是它的前n项和,
,则Sn最小时,n=_________
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b376aabb7d49ad8c8999eff8589c42b8.png)
您最近一年使用:0次
2018-10-13更新
|
650次组卷
|
2卷引用:青海省玉树州2019-2020学年高三联考数学(文)试题
名校
5 . 已知递减等差数列
中,
为
等比中项,若
为数列
的前
项和,则
的值为__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/98d35a377cdc45b6169bf2ba1a8b4a2c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fb9c3832ed2813b3bb952a28f094e4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e603b277aba781cf78b7adf8fc7f053f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/98d35a377cdc45b6169bf2ba1a8b4a2c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/194592cb77de8a597d5d64e1c85c3249.png)
您最近一年使用:0次
2017-12-15更新
|
716次组卷
|
3卷引用:【全国百强校】青海省西宁市第四高级中学、第五中学、第十四中学三校2019届高三4月联考数学(理)试题
名校
6 . 已知等差数列
中,
,
,则其通项公式![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3f7fda69e2b32b9ced2239f915fa59b.png)
__________
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/22c5c4ac959eb2c4b74afabc9cdd3a6b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c03d15d5cb7b49ecee2fe5e99fbaa75.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3f7fda69e2b32b9ced2239f915fa59b.png)
您最近一年使用:0次
2017-08-10更新
|
710次组卷
|
4卷引用:青海省海东市第二中学2019-2020学年高一下学期期中考试数学试题