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1 . 在数列的每相邻两项之间插入此两项的积,形成新的数列,这样的操作叫做该数列的一次“扩展”.将数列
进行“扩展”,第一次得到数列
;第二次得到数列
;….设第
次“扩展”后得到的数列为
,并记
,其中
,则数列
的前
项和为__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c8276d70443c3f3c3cbdf128fae8925c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a2303277c24a13d9f8ef622f841ca6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c2c9b3aad25029a97ef5e813d6c5a11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/58c96582b6ccd8520e7873a006c55cd3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f21439a5132fd2c138e242cf3ce9f9f3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1621bd4aa4545c1fe4c2196aa48efdb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
您最近一年使用:0次
2018-05-09更新
|
972次组卷
|
3卷引用:贵州省铜仁市伟才学校2019-2020学年高一下学期期中考试数学试题
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2 . 在
中,三内角
所对的边分别是
,若
依次成等比数列,
则
的取值范围是____ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/38335830b93ac4d99c28a8e209eecb3f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76f0649064a085fb74c997fb507a9b6d.png)
则
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d9ed77048c6f38345bf14e1ccb526fe1.png)
您最近一年使用:0次