已知实数
构成一个等差数列,则圆锥曲线
的焦距为__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35bafd58bd6c3625f61acf03c59e40a6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cfda0696f276fff4177533f8c63e349.png)
更新时间:2017-04-27 23:04:36
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【推荐1】已知数列
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【推荐2】已知两个等差数列
的前
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,且
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04e9d69f5f7d2e727d2cbc637e79cc7e.png)
_______ .
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解题方法
【推荐1】已知椭圆
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过椭圆的中心
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1b8b274e442d154084224abf73d7593d.png)
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【推荐2】已知双曲线
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