下列各函数中 最小值为2的是()A y=x+x分之一 B y=sinx+sinx分分之一 x属于（0

问题补充：

下列各函数中,最小值为2的是()A,y=x+x分之一,B,y=sinx+sinx分分之一,x属于（0,二分之π）C,y=根号（x平方+2）分之x平方+3,D,y=x+根号x分之2－1,为什么,B不是取不到等号吗?麻烦分析一下,

答案：

A的值域是(-∞,-2]∪[2,+∞)

B 0＜x＜π/2

0＜sinx＜1

所以值域是(2,+∞)

C y=(x^2+3)/√(x^2+2)=√(x^2+2)+1/√(x^2+2)

因为√(x^2+2)≥√2

所以值域是[3√2/2,+∞)

D y=x+2/√x-1=x+1/√x+1/√x-1≥3[x*(1/√x)*(1/√x)]^(1/3)-1=2

所以答案应该选D才对.

======以下答案可供参考======

供参考答案1:

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供参考答案2:

你用排除法 吧。

其他貌似都有可能=0

如果有=0 最小值就不是2

B。有说了个区间。。

所以不一样。