ý cậu là :A=(\(-\infty;m+1\)]\(;B=\left\{x\in R/2x+5\ge m\right\}\) ?
\(A\cap B=\varnothing\Leftrightarrow\left\{{}\begin{matrix}x>m+1\\2x+5\ge m\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}x>m+1\\x\ge\frac{m-5}{2}\end{matrix}\right.\)
Có \(m+1>\frac{m-5}{2}\) \(\Rightarrow A\cap B=\varnothing\Leftrightarrow m< x-1\)
\(\Leftrightarrow m\in\left(-\infty;x-1\right)\)