x2 |
4 |
y2 |
3 |
![](http://hiphotos.baidu.com/zhidao/pic/item/ac6eddc451da81cbd948407c5166d016082431d1.jpg)
∴a2=4,b2=3,可得c=
a2-b2 |
所以橢圓的離心率e=
c |
a |
1 |
2 |
a2 |
c |
作出橢圓的右準線l如圖,過M點作MN⊥l于N,
根據(jù)圓錐曲線的統(tǒng)一定義,得
|MF| |
|MN| |
1 |
2 |
∴2|MF|=|MN|,所以|MP|+2|MF|=|MP|+|MN|.
欲求|MP|+2|MF|的最小值,即求|MP|+|MN|的最小值,
過P(1,-1)作PN0⊥l于N0,交橢圓于M0,由平面幾何知識可得,當動點M在橢圓上運動,與點M0重合時,|MP|+2|MF|取到最小值.
設M0(x0,-1),代入橢圓方程得
x02 |
4 |
(-1)2 |
3 |
2
| ||
3 |
∴使|MP|+2|MF|的值最小的點M的坐標為(
2
| ||
3 |
故答案為:(
2
| ||
3 |