ï¼ä¸ï¼ã设P(ms-c,s)ï¼P(mh-c,h)ï¼ç±PãQå¨æ¤åä¸ï¼å³sãhæ¯æ¹ç¨ (mt-c)^2/a^2+t^2/b^2=1 çä¸¤æ ¹ï¼ç±é¦è¾¾å®çå¾ s+h=2mcb^2/(b^2*m^2+a^2) ï¼sh=-b^4/(m^2*b^2+a^2) ï¼åé AP=(ms-a-c,s) ï¼AQ=(mh-a-c,h) ï¼èåéAP ·åéAQ=(ms-a-c,s)·(mh-a-c,h)=(ms-a-c)(mh-a-c)+sh=(1/2)*(a+c)^2 ï¼å³ (m^2+1)*s*h-(a+c)*(s+h)+(1/2)*(a+c)^2=0 ï¼èç«æ¶å»sãhï¼å¹¶æ´çå¾ [(e+1)^2]*[(m^2-2)e^2+4e-(m^2+1)]=0ï¼0<e<1ï¼ï¼è§£å¾æ¤åCç离å¿ç e=[-2+â(m^4-m^2+2)]/(m^2-2) ã
ï¼äºï¼ãè¥ eâ(1/2,2/3) ï¼å³ 1/2<[-2+â(m^4-m^2+2)]/(m^2-2)]<2/3 ï¼0<3m^4-6m^2+7 ä¸ 5m^4-17m^2+14<0 ï¼è§£å¾ 7/5<m^2<2 ï¼mçåå¼èå´ {m|-â2<m<-â35/5 æ â35/5<m<â2} ã
ï¼ä¸ï¼ã)è¥ APâ©l=M ï¼AQâ©l=N ï¼å·¦å线lçæ¹ç¨ä¸º x=-a^2/c ï¼ç´çº¿APçåæ°æ¹ç¨ä¸º sx-(ms-a-c)y-sa=0 ï¼æ±å¾Mç纵åæ M_y=[(a^2+ac)*s]/(ac+c^2-mcs) ï¼åçå¾Nç纵åæ 为 N_y=[(c^2+ac)*h]/(ac+c^2-mch)ãM_y*N_y=(a^2+ac)^2*s*h/[(c^2+ac-mcs)*(c^2+ac-mch)]=(a^2+ac)^2*s*h/[(c^2+ac)^2-mc(c^2+ac)(s+h)+m^2*c^2*s*h]=(a^2+ac)^2*(-b^4)/[(c^2+ac)^2*(m^2*b^2+a^2)-2m^2*c^2*b^2*(c^2+ac)-b^4*m^2*c^2]=(a^2+ac)^2*(-b^4)/{(c^2+ac)^2*a^2+[(c^2+ac)^2-2*c^2*b^2*(c^2+ac)-b^4*c^2)]*m^2}=(a^2+ac)^2*(-b^4)/{(c^2+ac)^2*a^2+[(a+c)^2-2*(c^2+ac)-b^2]*b^2*c^2*m^2}=(a^2+ac)^2*(-b^4)/[(c^2+ac)^2*a^2]=-b^4/c^2ï¼æ以MãNç¹ç纵åæ ä¹ç§¯ä¸ºå®å¼-b^4/c^2ã
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