\[По\ теореме\ Виета:\]
\[x_{1} + x_{2} = - b;\ \ \ \ \]
\[x_{1} \cdot x_{2} = c.\]
\[x_{1} = - 3;x_{2} = 8:\]
\[x_{1} + x_{2} = 5;\]
\[x_{1} \cdot x_{2} = - 24.\]
\[\Longrightarrow x^{2} - 5x - 24 = 0\]