若
、
、
这三个的数字可适当排序后成为等差数列,也可适当排序后成等比数列,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85fcb8bb3febd7d44cc2460d6e806a77.png)
________________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d3b969cecfebfa770f2d15ffe66ceb6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85fcb8bb3febd7d44cc2460d6e806a77.png)
更新时间:2020-02-01 08:29:03
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适中
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名校
【推荐1】在正项等比数列
中,
,
是
,
的等差中项,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42e4487468ab2823d6dbf7f0ebd2eb38.png)
____ .
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解题方法
【推荐2】已知
和
都是等差数列,
的公差为
,且
,
,记
分别为数列
的前
项和,且
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c98c59cd4749afdd21e73529fc84323.png)
______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
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【推荐1】公差不为0的等差数列
的部分项
构成等比数列,且
,
,
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2a0196acf9408fe85205f287c3c7b81.png)
________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c3648ecf048e1dc0953390ad4ae41d1.png)
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解题方法
【推荐2】椭圆
的左右焦点分别为
为椭圆上位于x轴上方的两点,且满足
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构成公比为2的等比数列,则C的离心率为__________ .
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