Question

Answer 1

a) \(x^2-5x\ne0\Rightarrow\left\{{}\begin{matrix}x\ne0\\x\ne5\end{matrix}\right.\) 

   Vậy \(D=R\)\\(\left\{0,5\right\}\)

b) \(\left\{{}\begin{matrix}x+7\ge0\\x^2-2x-3\ne0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x\ge-7\\\left(x-3\right)(x+1)\ne0\end{matrix}\right.\)

                                  \(\Rightarrow\left\{{}\begin{matrix}x\ge-7\\x\ne3\\x\ne-1\end{matrix}\right.\)

   Vậy \(D=(-7;+\infty)\)\\(\left\{-1;3\right\}\)