| a2-b2 |
直线y=x-1代入椭圆
| x2 |
| m |
| y2 |
| m-1 |
设A(x1,y1),B(x2,y2),则x1+x2=
| 2m |
| 2m-1 |
| 2m-m2 |
| 2m-1 |
∴y1y2=(x1-1)(x2-1)=
| -m2+2m-1 |
| 2m-1 |
∵以AB为直径的圆过椭圆的左焦点F,∴
| FA |
| FB |
∴(x1+1,y1)•(x2+1,y2)=0
∴
| 2m-m2 |
| 2m-1 |
| 2m |
| 2m-1 |
| -m2+2m-1 |
| 2m-1 |
∴m2-4m+1=0
∴m=2±
| 3 |
∵m>1
∴m=2+
| 3 |
故答案为:2+
| 3 |
| x2 |
| m |
| y2 |
| m−1 |
| a2-b2 |
| x2 |
| m |
| y2 |
| m-1 |
| 2m |
| 2m-1 |
| 2m-m2 |
| 2m-1 |
| -m2+2m-1 |
| 2m-1 |
| FA |
| FB |
| 2m-m2 |
| 2m-1 |
| 2m |
| 2m-1 |
| -m2+2m-1 |
| 2m-1 |
| 3 |
| 3 |
| 3 |