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 |