\[2x + ac + cx + 2a =\]
\[= 2x + 2a + cx + ac =\]
\[= 2 \cdot (x + a) + c(x + a) =\]
\[= (x + a)(2 + c)\]
\[Проверка:\]
\[(x + a)(2 + c) =\]
\[= 2x + ac + cx + 2a\]
\[\Longrightarrow верно.\]