\[x² - (5a - 2)x + 6a^{2} - 4a = 0\]
\[= a^{2} - 4a + 4 =\]
\[= (a - 2)^{2} > 0;\ \ a \neq 2\]
\[x_{1} = \frac{5a - 2 + a - 2}{2} = \frac{6a - 4}{2} =\]
\[= 3a - 2\]
\[x_{2} = \frac{5a - 2 - a + 2}{2} = \frac{4a}{2} = 2a\]
\[\left\{ \begin{matrix} 4 \leq 3a - 2 \leq 7 \\ 4 \leq 2a \leq 7\ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} 6 \leq 3a \leq 9\ \\ 2 \leq a \leq 3,5 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} 2 \leq a \leq 3\ \ \ \ \\ 2 \leq a \leq 3,5 \\ \end{matrix} \right.\ \]
\[Ответ:(2;3\rbrack.\]