\[4x^{2} + 6x + k = 0;\ \ \ x_{1} = 5\]
\[x_{1} + x_{2} = - \frac{6}{4}\]
\[5 + x_{2} = - 1,5\]
\[x_{2} = - 6,5.\]
\[x_{1} \cdot x_{2} = \frac{k}{4}\]
\[5 \cdot ( - 6,5) = \frac{k}{4}\]
\[k = - 130.\]
\[Ответ:x_{2} = - 6,5;\ \ k = - 130.\]