\[\frac{\left( x^{2} + 5x \right)}{2} - 3 = 0\ \ \ | \cdot 2\]
\[x^{2} + 5x - 6 = 0\]
\[x_{1} + x_{2} = - 5;\ \ x_{1} \cdot x_{2} = - 6\]
\[x_{1} = - 6;\ \ x_{2} = 1.\]
\[Ответ:x = - 6;x = 1.\]