\[3x^{2} - (7a + 2)x + 2a^{2} + 4a = 0\]
\[= 25a^{2} - 20a + 4 = (5a - 2)^{2};\ \ \]
\[a \neq \frac{2}{5}\]
\[x_{1} = \frac{7a + 2 + 5a - 2}{6} =\]
\[= \frac{12a}{6} = 2a\]
\[x_{2} = \frac{7a + 2 - 5a + 2}{6} =\]
\[= \frac{2a + 4}{6} = \frac{1}{3}a + \frac{2}{3}\]
\[Ответ:нет\ таких\ значений.\]