<br /> \begin{array}{l}:a^2 + b^2 + c^2 = 1 \\ <br /> Then: \\ <br /> \frac{{a^3 }}{{2b^2 + c^2 }} + \frac{{b^3 }}{{2c^2 + a^2 }} + \frac{{c^3 }}{{2a^2 + b^2 }} \ge 1 \\ <br /> \end{array}<br />