1. x,y,z,a,b,c dương.
CMR: $\sqrt[3]{abc}+\sqrt[3]{xyz}\leq \sqrt[3]{(a+x)(b+y)(c+z)}$
2. a,b,c,d dương.
CMR: $\sum \sqrt{\frac{a}{b+c+d}} > 2$
3. a,b,c dương.
CMR: $\frac{1}{a^{3}+b^{3}+abc}+\frac{1}{b^{3}+c^{3}+abc}+\frac{1}{c^{3}+a^{3}+abc}\leq \frac{1}{abc}$
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