题目内容
(本题满分14分) 若F1、F2为双曲线
的左、右焦点,O为坐标原点,P在双曲线左支上,M在右准线上,且满足
(Ⅰ)求此双曲线的离心率;(Ⅱ)若此双曲线过点
,求双曲线方程;(Ⅲ)设(Ⅱ)中双曲线的虚轴端点为B1,B2(B1在y轴正半轴上),求B2作直线AB与双曲线交于A、B两点,求
时,直线AB的方程.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115503764511.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155038271323.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115503998461.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504139376.gif)
(Ⅰ)
(Ⅱ)
(Ⅲ)![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504217452.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504185230.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504201497.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504217452.gif)
解:(Ⅰ)由
知四边形PF1OM为平行四边形,又由![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155042631034.gif)
知
为菱形,设半焦距为c,由
,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155043571701.gif)
(Ⅱ)
双曲线方程为
代入,
有
即所求双曲线方程为
(Ⅲ)依题意得B1(0,3),B2(0,-3).设直线AB的方程为![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504482739.gif)
则由
∵双曲线的渐近线为
时,AB与双曲线只有一个交点,即
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504622826.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155046531541.gif)
又![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155046691020.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504685725.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504700964.gif)
直线AB的方程为![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504217452.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504232498.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155042631034.gif)
知
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504310758.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504341528.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155043571701.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504404583.gif)
(Ⅱ)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504419462.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504435780.gif)
有
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504451620.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504201497.gif)
(Ⅲ)依题意得B1(0,3),B2(0,-3).设直线AB的方程为
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504482739.gif)
则由
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155044971242.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504544589.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504607305.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504622826.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155046531541.gif)
又
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155046691020.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504685725.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504700964.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504716308.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115504217452.gif)
![](http://thumb.zyjl.cn/images/loading.gif)
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