\[x^{3} < x^{- 3}\]
\[так\ как\ \ \ x^{- 3} = \frac{1}{x^{3}};\ \ \ \ \ \ x < - 1.\]
\[Пример:\ \ x = - 2.\]
\[x^{3} = ( - 2)^{3} = - 8;\text{\ \ \ \ \ }\]
\[x^{- 3} = \frac{1}{x^{3}} = \frac{1}{- 8} \Longrightarrow \ - 8 < - \frac{1}{8}.\]