解ï¼è§ä¸å¾ãå°æç©çº¿æ¹ç¨ä»£å ¥åæ²çº¿æ¹ç¨ä¸ï¼æ¹ç¨ä¸¤è¾¹åæ¶ä¹ä»¥ï¼ab)^2,æï¼
1ãæ±Pç¹åæ ï¼b^2x^2-2pa^2x-(ab)^2=0........(1); (p/2)=c,p=2c.....(2)
â³=(-2pa^2)^2-4b^2[-(ab)^2]=4a^2[(pa)^2+b^4]=4a^2[4(a^2+b^2)a^2+b^4]
=[2a(2a^2+b^2)]^2;
x1,2={2pa^2+/-2a(2a^2+b^2)}/(2b^2)(åæ£æ°ï¼è´å¼èå»ï¼
Px=[pa^2+a(2a^2+b^2)]/b^2=[2ca^2+a(2a^2+b^2)]/b^2;
Py=+/-â(2px)=+/-2âcx; å¾Pç¹åæ ï¼ï¼Px,Py)
2ãæ±eï¼PF1=â[(c-Px)^2+(0-Py)^2]=â[(c-Px)^2+(4cPx)].......(3)
ä¾é¢æï¼1/cos^2â PF1F2=(PF1)^2/(c-Px)^2=1+(4cPx)/(c-Px)^2=(7/5)^2=1+24/25
4cPx*25=24(c^2-2cPx+Px^2); 6Px^2-37cPx+6c^2=(Px-6c)(6Px-c)=0
Px1=6c,Px2=c/6;
6cb^2=2ca^2+a(2a^2+b^2); 2c(3b^2-a^2)=a(2a^2+b^2)....(4);
å¾ï¼e=c/a=(2a^2+b^2)/(6b^2-2a^2)=2,3,â2,â3;(ç»éªè¯ï¼æ²¡æ符åæ¡ä»¶ççæ¡ãï¼
3ã计ç®eçå¼ï¼e(6b^2-2a^2)=2a^2+b^2;(6e-1)b^2=(2e+2)a^2;b^2=(2e+2)a^2/(6e-1);
a^2+b^2=a^2[1+(2e+2)/(6e-1)a^2;æ¹ç¨ä¸¤è¾¹åæ¶é¤ä»¥a^2,å¾ï¼
e^2=(a^2+b^2)/a^2=(8e+1)/(6e-1); e^2(6e-1)=8e+1;å³ï¼6e^3-e^2-8e-1=0;
6e^3-e^2-7e-(e+1)=e(6e^2-e-7)-(x+1)=e(6e-7)(e+1)+(e+1)=(e+1)(6e^2-7e-1)=0;
e=-1(ä¸åçï¼èå»ï¼ï¼åï¼(6e^2-7e-1)=0ï¼e=(7+/-â73)/12å 为e>0,e=(7+â73)/12;
cb^2/6=2ca^2+a(2a^2+b^2);c(b^2-12a^2)=6a(2a^2+b^2)ï¼
e=c/a=6(2a^2+b^2)/(b^2-12a^2);æï¼e(b^2-12a^2)=12a^2+6b^2;
(e-6)b^2=12(e+1)a^2; c^2=a^2+b^2=[1+12(e+1)/(e-6)]a^2=(13e+6)a^2/(e-6)
e^2(e-6)-(13e+6)=e^3-6e^2-13e-6=e(e-7)(e+1)-(e+1)=(e+1)(e^2-7e-1)=0;
åçï¼e=(7+/-4â3)/2;e=(7+4â3)/2ã
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