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ï¼a+aå¹³æ¹åä¹1)(b+bå¹³æ¹å
ä¹1ï¼ï¼ä½ çéäºï¼å°±æ¯
a,bâR+ï¼a+b=1,æ±(a+1/a^2)(b+1/b^2)çæå°å¼
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(a+1/a^2)(b+1/b^2)
=ab+b/a^2+a/b^2+1/a^2b^2
=(a^3b^3+b^3+a^3+1)/a^2b^2
=[a^3b^3+(a+b)(a^2-ab+b^2)+1]/a^2b^2
=(a^3b^3+a^2-ab+b^2+1)/a^2b^2
=[a^3b^3+(a+b)^2-2ab-ab+1]/a^2b^2
=(a^3b^3-3ab+2)/a^2b^2
令ab=t
1=a+bâ¥2â(ab)
æ以â(ab)<=1/2
0<abâ¤1/4
â´0<tâ¤1/4
=(t^3-3t+2)/t^2
=t-3/t+2/t^2
æ±å¯¼
y'=1+3/t^2-4/t^3=0
t^3+3t-4=0
t=1
æ以å½tâ¤1æ¶
å½æ°åè°éå
å³å¨t=1/4æ¶åå°æå°å¼
å³=1/4-3*4+2*4^2
=1/4-12+32
=81/4
æ¤æ¶a=b=1/2
æ°é«ä¸è¿æ²¡å¦å½æ°ï¼è½ä¸è½åªç¨ä¸çå¼å?
去死吧你,当a=b=2分之1时,原式等于4分之81!