(1)æ ¹æ®é¢æ
|PM|=Rp+Rm
|PN|=Rn-Rp
â´|PM|+|PN|=Rm+Rn=1+5=6
|MN|=2
â´Pç轨迹为以(-1,0),(1,0)为ç¦ç¹çæ¤åæ¹ç¨x²/9+y²/8=1
(2)设A(x1,y1),B(x2,y2),ç´çº¿l1为y=k(x-1)+8/3 kâ 0 åå¦ä¸ç´çº¿l2为y=-k(x-1)+8/3ï¼ä»£å
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8x²+9[k²x²+2kx(8-3k)/3+(8-3k)²/9]=72 æ´çå¾
(9k²+8)x²+6kx(8-3k)+(9k²-48k-8)=0 â´ x1=(9k²-48k-8)/(9k²+8) ,y1=-(48k²-16k)/(9k²+8)+8/3
åçl2代å
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8x²+9[k²x²-2kx(8+3k)/3+(8+3k)²/9]=72æ´çå¾
(9k²+8)x²-6kx(8+3k)+(9k²+48k-8)=0 â´ x2=(9k²+48k-8)/(9k²+8) ,y2=-(48k²-16k)/(9k²+8)+8/3
å¯ä»¥çåºy1=y2,å³A,Bç纵åæ ç¸çï¼å æ¤ç´çº¿ABæç为0
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