äºæ¬¡å½æ°y=ax^2+bx-4m(a>0)å¾åä¸Yè½´è´å轴交äºç¹Bï¼0ï¼-4m),m>0,
æ£æ¹å½¢ABCDçè¾¹ADä¸yè½´æ£å轴交äºEï¼0ï¼m),
â´OA^=OB*OE=4m^,OA=2m,A(-2m,0).
(2)æâ³BAOç»Bæ转è³â³BCO',
åBO'â¥yè½´ï¼BO'=BO=4m,O'C=OA=2m,
â´O'(4m,-4m),C(4m,-2m).
y=ax^2+bx-4m(a>0) ä¸xè½´çå¦ä¸ä¸ªäº¤ç¹ä¸ºFï¼ä¸CFåç´äºxè½´,
â´F(4m,0),
â´ax^2+bx-4m=a(x+2m)(x-4m)=ax^2-2amx-8m^2,
æ¯è¾å¸¸æ°é¡¹å¾-4m=-8m^2,m>0,m=1/2.
(3)ç´çº¿AB:y=-2x-4mä¸æç©çº¿y=x^2+bx-4m交äºB(0,-4m),G(-b-2,*)
ç´çº¿BD:y=(1/2)x-4mä¸æç©çº¿y=x^2+bx-4m交äºB(0,-4m),H(1/2-b,*)
äºæ¬¡å½æ°y=x^2+bx-4mçå¾åè¿ç¹B,ä¸æ£æ¹å½¢çåæ¡è¾¹ï¼å
æ¬ç«¯ç¹ï¼å§ç»é½æäºä¸ªäº¤ç¹,
<==>G,Håå«å¨è¾¹AB,BDçå
é¨ï¼
<==>-2m<-b-2<0<1/2-b<4m,
â´-2<b<1/2,为æ¤ï¼4m<=1/2-(-2),åm>0,
â´0<m<=5/8,为ææ±ã
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