（2）由（1）可得F1(?2,0)，设A(x1,y1),B(x2,y2)，M(x3,y3),N(x4,y4)， 可得AQ：y?y1x?1(x?1)?x?1y?1， x1?1y1?x2y2??1?5?x1?12x1?1?95?y?y?4?0， ∴联立方程?2x?1yy11?x?1y?1?y1??4y124y124y1∴y1y3?，∴y3?， ?5?x1x1?5x1?5∴x3?x1?15x?95x?94y1，∴M(1y3?1?1,)
y1x1?5x1?5x1?55x2?94y2,) x2?5x2?5同理，直线BQ与椭圆交点N的坐标为N(4y14y2?y?y14y1(x2?5)?4y2(x1?5)x?5x2?5∴k2?3 ?1?x3?x45x1?9?5x2?9(5x1?9)(x2?5)?(5x2?9)(x1?5)x1?5x2?5?4y1(x2?5)?4y2(x1?5)y1x2?y2x1?5(y2?y1)?
16(x2?x1)4(x2?x1)?y1?k1(x1?2)设AB：y?k1(x?2)，∴?
y?k(x?2)?212代入可得
k2?k1(x1?2)x2?k1(x2?2)x1?5(y2?y1)2k1(x2?x1)?5(y2?y1)?
4(x2?x1)4(x2?x1)?15y?y1157k1??2?k1?k1?k1， 24x2?x1244k14?为定值. k27∴
