\[x^{2} + 7x + 12 = 0\]
\[x_{1} + x_{2} = - 7;\ \ x_{1} \cdot x_{2} = 12\]
\[x_{1} = - 4;\ \ \ x_{2} = - 3.\]
\[Ответ:x = - 4;x = - 3.\]