`~rai~`
\(\text{Câu 1:}x^2+1=\dfrac{1}{\sqrt{x-1}}\\ĐKXĐ:\begin{cases}x-1\ge 0\\\sqrt{x-1}\ne 0\end{cases}\\\Leftrightarrow x-1>0\\\Leftrightarrow x>1.\\TXĐ:D=(1;+\infty)\\\to\text{Chọn ý C.}\\\text{Câu 2:}\sqrt{x-5}=\sqrt{5-x}\\ĐKXĐ:\begin{cases}x-5\ge 0\\5-x\ge 0\end{cases}\\\Leftrightarrow \begin{cases}x\ge 5\\x\le 5\end{cases}\\\Leftrightarrow x=5.\\TXĐ:D=\{5\}.\\\to\text{Chọn ý D.}\)