1 . 设点
,过点F作斜率为k的直线l交椭圆
于C,D两点.
(1)记直线
的斜率分别为
.从下列①②③三个式子中任选其一,当k变化时,判断该式子是否为定值,若是,求出定值;若不是,请说明理由.
①
;②
;③
.
(2)当直线
分别交双曲线
的下支于P,Q两点(异于点B)时,求
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20421239f70724807fc2e42f74b1f02d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f182db8ffa0d36588407eae8aeb7aa92.png)
(1)记直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5913ac8f576f9389802005ae712205d0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c65902e35640cf2c8d4111c36b40145.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b881044b5c73db6fcce110525741b02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89c20aa9e89d8cc15be390051124ee5d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0601dc0a83ff1c3b01dce7cdaa18cabb.png)
(2)当直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2013303974d530fce9a9930938f4c2b6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2aea802c49af59b44b8de07f6ef56d90.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411e6e928c39bb54f031aa3e5d492852.png)
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名校
2 . 已知点
为椭圆
的右焦点,椭圆的离心率为
,过点
的直线
交椭圆于
两点(点
在
轴的上方),且
,则直线
的斜率为__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7dd54b9df3402ad91e2d34c40efe0c7a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/860884c0017c8bceb5b0edff796c144f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c74a907dda6bb7d9d56d009d9df253.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b2171a7e806dc496b06bfe0a3a043e1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
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