(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∴
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