Tìm x biết: (x – 3)(x – 4) > 0
Giải thích
(x – 3)(x – 4) > 0
⇔ \[\left[ \begin{array}{l}\left\{ \begin{array}{l}x - 3 > 0\\x - 4 > 0\end{array} \right.\\\left\{ \begin{array}{l}x - 3 < 0\\x - 4 < 0\end{array} \right.\end{array} \right.\]
⇔ \[\left[ \begin{array}{l}x > 4\\x < 3\end{array} \right.\]