已知实数a+b+c=2 abc=4 求a、b、c中的最大者的最小值? 怎么做啊?

谢谢哦!!
2024-12-02 03:05:13
推荐回答(2个)
回答1:

数学思想最重要
由a+b+c=2得:a
,b,c中至少有一正。
再由abc=4得:
a,b,c皆不为0,且是一正两负
(不可能是三正。因为三正的话,有(a+b+c)/3>=三次根号内abc 即 :2/3>=4开立方>1.矛盾)
不妨设a为正
则a为最大值。
得b+c=2-a<0(1),bc=4/a>0(2)b,c
可视为方程x^2-(2-a)x+4/a=0的两实数根。
则delta=(2-a)^2-16/a>=0(3)
由(1)(2)(3)可解得a>=4所以,a,b,c中最大都的最小值为4
而b、c同理

回答2:

已知实数a、b、c满足a+b+c=2,abc=4,求a、b、c中最大者的最小值

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