bat dang thuc lop 10 hay

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thanhliuhp

[TEX]a+b+c=1[/TEX] \Rightarrow [TEX]abc\leq\frac{1}{27}[/TEX]
\Rightarrow [TEX]\sqrt[3]{(abc)^2} \geq 3abc[/TEX]
\Rightarrow [TEX]ab+bc+ac \geq 3\sqrt[3]{(abc)^2} \geq 9abc >\frac{18abc}{2+abc}[/TEX]
(do [TEX]abc>0[/TEX])
 
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