ĐKXĐ:
a/ \(\left\{{}\begin{matrix}x+1\ne0\\\frac{x+1}{x}\ge0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x< -1\\x>0\end{matrix}\right.\)
b/ \(2x^2-3x-4\ge0\Rightarrow\left[{}\begin{matrix}x\le\frac{3-\sqrt{41}}{4}\\x\ge\frac{3+\sqrt{41}}{4}\end{matrix}\right.\)