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nguyenthitramy93


cho a, b,c>0, [TEX] a^2+ b^2+ c^2=3[/TEX] Chứng minh:
[TEX]{\frac{1}{a+b}}+\frac{1}{b+c}+ \frac{1}{c+a}\geq\frac{4}{a^2+7}+\frac{4}{b^2+7} +\frac{4}{c^2+7}[/TEX]
[TEX]{\frac{1}{a+b}}+\frac{1}{b+c}+ \frac{1}{c+a}\geq\frac{4}{a^2+7}+\frac{4}{b^2+7} +\frac{4}{c^2+7}[/TEX]