a, ĐKXĐ : \(\left\{{}\begin{matrix}\frac{x^2}{x+1}\ge0\\x+1\ne0\end{matrix}\right.\)
=> \(\left\{{}\begin{matrix}x+1\ge0\\x+1\ne0\end{matrix}\right.\)
=> x + 1 > 0
=> x > - 1 .
b, ĐKXĐ : \(\left\{{}\begin{matrix}x\ge0\\\sqrt{x}+1\ge0\end{matrix}\right.\)
=> \(x\ge0\)