06选择题4★★☆☆☆
已知 a>0,b>0a > 0, b > 0, 则 ( )
A.
a2+b2>2aba^2 + b^2 > 2ab
B.
1a+1b1ab\frac{1}{a} + \frac{1}{b} \ge \frac{1}{ab}
C.
a+b>aba + b > \sqrt{ab}
D.
1a+1b2ab\frac{1}{a} + \frac{1}{b} \le \frac{2}{\sqrt{ab}}
答案与解析

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