Để B có nghĩa thì \(2m+1\ge m\Rightarrow m\ge-1\)
Để \(A\backslash B=A\Leftrightarrow A\cap B=\varnothing\)
\(\Rightarrow\left[{}\begin{matrix}m>3\\2m+1< -3\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}m>3\\m< -2\left(l\right)\end{matrix}\right.\) \(\Rightarrow m>3\)