\[x² + 5x + k = 0\ \ \ \ \ и\ \ \ \ x_{1} = - 2\]
\[x_{1} + x_{2} = - 5 \Longrightarrow - 2 + x_{2} =\]
\[= - 5 \Longrightarrow x_{2} = - 3\]
\[x_{1} \cdot x_{2} = k \Longrightarrow - 3 \cdot ( - 2) =\]
\[= k \Longrightarrow k = 6.\]