爱情走过学不会
幼苗
共回答了15个问题采纳率:86.7% 举报
设双曲线
![](https://img.yulucn.com/upload/7/aa/7aa171350723125ff8b263253408c49a_thumb.jpg)
的两个焦点分别为
![](https://img.yulucn.com/upload/e/e1/ee15511096965f76a5e126fd5fa7598c_thumb.jpg)
、
![](https://img.yulucn.com/upload/a/40/a40f15e75d9a96f5afb5bc3bef0a410d_thumb.jpg)
,离心率为2.
(1)求双曲线的渐近线方程;
(2)过点
![](https://img.yulucn.com/upload/9/04/904826417906336ad5a06dd97fcaaeea_thumb.jpg)
能否作出直线
![](https://img.yulucn.com/upload/1/65/1658b7801aeb3e62bb0e9a7558b9fc85_thumb.jpg)
,使
![](https://img.yulucn.com/upload/1/65/1658b7801aeb3e62bb0e9a7558b9fc85_thumb.jpg)
与双曲线
![](https://img.yulucn.com/upload/d/03/d032b6bc793ba83d485fbe70dad6e47b_thumb.jpg)
交于
![](https://img.yulucn.com/upload/7/3f/73f37562283bf3cc957f877c4f14db8a_thumb.jpg)
、
![](https://img.yulucn.com/upload/c/ba/cba1d9da6b3793c0f9180259382698b1_thumb.jpg)
两点,且
![](https://img.yulucn.com/upload/b/06/b069aabf17bdcb3af9aa30d4e5e23948_thumb.jpg)
,若存在,求出直线方程,若不存在,说明理由.
(1)∵
![](https://img.yulucn.com/upload/f/26/f268d6959cdb0342ce53ab0a8c2e0f36_thumb.jpg)
∴
![](https://img.yulucn.com/upload/7/8e/78e2ee53ec3279f0fe90419647c72d15_thumb.jpg)
∴ 双曲线渐近线方程为
(2)假设过点
![](https://img.yulucn.com/upload/9/04/904826417906336ad5a06dd97fcaaeea_thumb.jpg)
能作出直线
![](https://img.yulucn.com/upload/1/65/1658b7801aeb3e62bb0e9a7558b9fc85_thumb.jpg)
,使
![](https://img.yulucn.com/upload/1/65/1658b7801aeb3e62bb0e9a7558b9fc85_thumb.jpg)
与双曲线
![](https://img.yulucn.com/upload/d/03/d032b6bc793ba83d485fbe70dad6e47b_thumb.jpg)
交于
![](https://img.yulucn.com/upload/7/3f/73f37562283bf3cc957f877c4f14db8a_thumb.jpg)
、
![](https://img.yulucn.com/upload/c/ba/cba1d9da6b3793c0f9180259382698b1_thumb.jpg)
两点,
且
![](https://img.yulucn.com/upload/b/06/b069aabf17bdcb3af9aa30d4e5e23948_thumb.jpg)
若过点
![](https://img.yulucn.com/upload/9/04/904826417906336ad5a06dd97fcaaeea_thumb.jpg)
的直线斜率不存在,则不适合题意,舍去.
设直线
![](https://img.yulucn.com/upload/1/65/1658b7801aeb3e62bb0e9a7558b9fc85_thumb.jpg)
方程为
①代入②得:
∵
![](https://img.yulucn.com/upload/b/06/b069aabf17bdcb3af9aa30d4e5e23948_thumb.jpg)
∴
![](https://img.yulucn.com/upload/5/53/5531a3f97fb08866936f054b97cd362e_thumb.jpg)
∴
∴
![](https://img.yulucn.com/upload/0/84/08418bf0116aa84956cd3fc26a89a04b_thumb.jpg)
∴
![](https://img.yulucn.com/upload/9/f4/9f4061eef2f1f79eccf0dd789ca69f44_thumb.jpg)
不合题意.∴ 不存在这样的直线.
(1)根据离心率先求出a
2 的值,然后令双曲线等于右侧的1为0,解此方程可得双曲线的渐近线方程.
(2)设直线l的方程为
![](https://img.yulucn.com/upload/9/e7/9e7b3aa174f3f2b54bb242fc39492555_thumb.jpg)
,然后直线方程与双曲线方程联立,消去y,得到关于x的一元二次方程,利用韦达定理
![](https://img.yulucn.com/upload/b/06/b069aabf17bdcb3af9aa30d4e5e23948_thumb.jpg)
表示此条件,得到关于k的方程,解出k的值,然后验证判别式是否大于零即可.
1年前
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