B/t A có nghĩa \(\Leftrightarrow\left\{{}\begin{matrix}x-3\ge0\\4-x>0\end{matrix}\right.\) \(\Leftrightarrow3\le x< 4\)
B/t B có nghĩa \(\Leftrightarrow\left\{{}\begin{matrix}x-1>0\\x^2-4x+4>0\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x>1\\\left(x-2\right)^2>0\end{matrix}\right.\) \(\Leftrightarrow2\ne x>1\)