:(2a)(2c).(2a>2c)2

,..1: xy?

X=ay=b

2 -xx,-yy,?-xx,-yy,?3 P(x,y),(-x,y)? (x,-y)?(-x,-y)?4 ??

XY5 ?

,:

-xx,,y;-yy,,x;-xx,-yy,,.

,XY( ) A.x2=4y B.x2+2xy+y=0 C.x2-4y2=5x D.9x2+y2=4D

, .:A1(-a,0) A2(a,0) B1(0,-b)B2(0,b)A1A2

B1B2?,

OB2F2,,.

, ,?

[1] a > c > 01 >e >0[2]1e 1c a b2e 0c 0 b3e =0 a = b c=0

.

e: 0 0

x y x y (a,0) (0,b)(0,a) (b,0)

{1}abce{2}{3}

116x2+25y2=400,.:

,(-3,0),(3,0)(-5,0)(5,0)(0,4)(0,-4)2a=10,2b=8:=2a=2b

2 : (1)(-3,0)(0,-2); (2)20,0.6

: (1),,,a=3,b=2

(2), 2a=20,e=0.6a=10,c=6b=8x,y,:

:13P302201 34x2+9y2=36

1OFA6cosOFA=2/3OFCb,ca cosOFA=e=c/a

3 ,,F2.A439km,B2384km,F2,A,B,6371km,(1km).

:,,A,B,F2x,F2(F1).