\[(a - 1)x² - 2ax + 3a = 0\]
\[D = 4a^{2} - 12a^{2} + 12a =\]
\[= - 8a^{2} + 12a < 0\]
\[- 8a^{2} + 12a = 0\]
\[- 4a(2a - 3) = 0\]
\[a = 0,\ \ a = 1,5\]
\[Ответ:( - \infty;0) \cup (1,5; + \infty).\]