CM rằng :$\frac{a+b}{ab+c^{2}}+\frac{b+c}{bc+a^{2}}+\frac{a+c}{ca+b^{2}}$ $\leq $ $\frac{1}{a}+\frac{1}{b}+\frac{1}{c}$
CM rằng :$\frac{a+b}{ab+c^{2}}+\frac{b+c}{bc+a^{2}}+\frac{a+c}{ca+b^{2}}$ $\leq $ $\frac{1}{a}+\frac{1}{b}+\frac{1}{c}$
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