Đáp án:
$\begin{gathered} 4{x^2} - 9{y^2} - 6y - 1 \hfill \\ = 4{x^2} - (9{y^2} + 6y + 1) \hfill \\ = {(2x)^2} - {(3y + 1)^2} \hfill \\ = \left[ {2x - (3y + 1)} \right]\left[ {2x + (3y + 1)} \right] \hfill \\ = (2x - 3y - 1)(2x + 3y + 1) \hfill \\ \end{gathered} $
