\[3x² + kx + 10 = 0\ \ \ \ и\ \ \ \ x_{1} = - 2\]
\[x² + \frac{k}{3}x + \frac{10}{3} = 0\]
\[x_{1} + x_{2} = - \frac{k}{3} \Longrightarrow - 2 - 1\frac{2}{3} =\]
\[= - \frac{k}{3} \Longrightarrow - 3\frac{2}{3} = - \frac{k}{3} \Longrightarrow k = 11\]
\[x_{1} \cdot x_{2} = \frac{10}{3} \Longrightarrow - 2 \cdot x_{2} =\]
\[= \frac{10}{3} \Longrightarrow x_{2} = - \frac{10}{6} = - 1\frac{2}{3}.\]