\[5x^{2} - 7x + k = 0\ \ \ \ и\ \ \ \ x_{1} = - 2\]
\[x² - \frac{7}{5}x + \frac{k}{5} = 0\]
\[x_{1} + x_{2} = \frac{7}{5} \Longrightarrow - 2 + x_{2} =\]
\[= 1,4 \Longrightarrow x_{2} = 3,4\]
\[x_{1} \cdot x_{2} = \frac{k}{5} \Longrightarrow - 2 \cdot 3,4 =\]
\[= \frac{k}{5} \Longrightarrow - 6,8 = \frac{k}{5} \Longrightarrow k = - 34.\]