\[- 50a^{2} + 25ax = 25a( - 2a + x)\]
\[Проверка:\ \]
\[25a( - 2a + x) = - 50a^{2} + 25ax\]
\[- 50a^{2} + 25ax = - 50a^{2} + 25ax\]
\[\Longrightarrow верно.\]