a) ĐK: $\left\{ \begin{array}{l} x+3\ge0 \\ x+1\ne0\\5-x>0 \end{array} \right .$
$\Leftrightarrow\left\{ \begin{array}{l} x\ge-3 \\ x\ne-1\\x<5 \end{array} \right .$
$\Leftrightarrow \left\{ \begin{array}{l} -3\le x<5 \\ x\ne-1 \end{array} \right .$
b) ĐK: $\left\{ \begin{array}{l}x-2\ge0\\ 2-x\ge0\end{array} \right .\Leftrightarrow \left\{ \begin{array}{l} x\ge2 \\ x\le2 \end{array} \right .$
$\Leftrightarrow x=2$
c) ĐK: $\left\{ \begin{array}{l}x+2\ne0\\ x-3\ne0\end{array} \right .\Leftrightarrow \left\{ \begin{array}{l} x\ne-2 \\ x\ne3 \end{array} \right .$
