\[x² - 2x - 8 < 0\]
\[x^{2} - 2x - 8 = 0\]
\[x_{1} + x_{2} = 2;\ \ x_{1} \cdot x_{2} = - 8\]
\[x_{1} = - 2;\ \ \ \ \ x_{2} = 4\]
\[(x + 2)(x - 4) < 0\]
\[Ответ:( - 2;4).\]