2025 Beijing Question 6 Single-choice Differentiating 2025_北京卷 (2025) 6.已知 $a>0, b>0$ ,则 A. $a^{2}+b^{2}>2 a b$B. $\frac{1}{a}+\frac{1}{b} \geq \frac{1}{a b}$C. $a+b>\sqrt{a b}$D. $\frac{1}{a}+\frac{1}{b} \leq \frac{2}{\sqrt{a b}}$ Answer keyC ☆ SaveCan't do it, show the explanation查看原卷 →