ĐKXĐ:
a/ \(\left\{{}\begin{matrix}2-x\ge0\\x\ne0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x\le2\\x\ne0\end{matrix}\right.\)
b/ \(\left\{{}\begin{matrix}x\ge0\\x^2-1\ge0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x\ge0\\\left[{}\begin{matrix}x\ge1\\x\le-1\end{matrix}\right.\end{matrix}\right.\) \(\Rightarrow x\ge1\)