B
bigbang195


cho các số [TEX]a,b >0.[/TEX] Chứng minh
[TEX]\frac{1}{a}+\frac{1}{b} \ge \frac{4}{a+b}[/TEX]
[TEX]\frac{1}{a}+\frac{1}{b}+\frac{1}{c} \ge \frac{9}{a+b+c}[/TEX]
:-SS
[TEX]\frac{1}{a}+\frac{1}{b} \ge \frac{4}{a+b}[/TEX]
[TEX]\frac{1}{a}+\frac{1}{b}+\frac{1}{c} \ge \frac{9}{a+b+c}[/TEX]
:-SS