N
ntlan0198


cho $x, y, z > 0$ và $xyz = 1$
cm:
$\frac{1}{1 + x^3 + y ^3} + \frac{1}{1 + y^3 + z^3} + \frac{1}{1 + z^3 + x^3}$ \leq $1$
cm:
$\frac{1}{1 + x^3 + y ^3} + \frac{1}{1 + y^3 + z^3} + \frac{1}{1 + z^3 + x^3}$ \leq $1$
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