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Posted: **Tue Apr 22, 2008 2:30 pm**

Fie \( x_1,x_2,....,x_n \geq -1 \) si \( \sum_{i=1}^{n} {x_i^3} =0 \).

Sa se arate ca: \( \sum_{i=1}^{n} {x_i} \leq 1 \) , unde \( n \in N* \).

Posted: **Sat Aug 30, 2008 11:06 am**

\( \sum_{i=1}^{n}{(x_i+1)(x_i^2-x_i+\frac{1}
{2})}\ge 0 \)

O inegalitate cu numere care au suma cuburilor nula