ĐKXĐ: \(\left\{{}\begin{matrix}\frac{x+1}{5x+2}\ge0\\5x+2\ne0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}\left\{{}\begin{matrix}x+1\ge0\\5x+2>0\end{matrix}\right.\\\left\{{}\begin{matrix}x+1< 0\\5x+2< 0\end{matrix}\right.\end{matrix}\right.\\5x\ne-2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}\left\{{}\begin{matrix}x\ge1\\x>-\frac{2}{5}\end{matrix}\right.\\\left\{{}\begin{matrix}x< 1\\x< -\frac{2}{5}\end{matrix}\right.\end{matrix}\right.\\x\ne-\frac{2}{5}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}x\ge1\\x< -\frac{2}{5}\end{matrix}\right.\\x\ne-\frac{2}{5}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x\ge1\\x< -\frac{2}{5}\end{matrix}\right.\)
