a: ĐKXĐ: (x-2)(x+1)<>0 và x+1<>0
=>\(x< >-1\)
b: ĐKXĐ: \(\left\{{}\begin{matrix}\dfrac{x}{1-x}>=0\\2x-1>=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}0< =x< 1\\x>=\dfrac{1}{2}\end{matrix}\right.\)
c: ĐKXĐ: 5-2x>=0 và 3-x(x+2)<>0
\(\Leftrightarrow\left\{{}\begin{matrix}x< =\dfrac{5}{2}\\x^2+2x-3< >0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x< =\dfrac{5}{2}\\x\notin\left\{-3;1\right\}\end{matrix}\right.\)