\[4x^{2} - 12x = 0\]
\[4x \cdot (x - 3) = 0\]
\[x = 0\ \ \ или\ \ \ x - 3 = 0\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = 3\]
\[Ответ:x = 0;x = 3.\ \]