\[(9 - 3a)x² - (a - 3)x + 1 = 0\]
\[при\ a = 3,\]
\[0 \cdot x - 0 + 1 = 0 - нет\ корней\]
\[D = a^{2} - 6a + 9 - 36 + 12a =\]
\[= a^{2} + 6a - 27 < 0\]
\[a^{2} + 6a - 27 = 0\]
\[a_{1} + a_{2} = - 6,\ \ a_{1} \cdot a_{2} = - 27\]
\[a_{1} = - 9,\ \ a_{2} = 3\]
\[Ответ:( - 9;3\rbrack.\]