Answer
$D=\{(x,y)\in\mathbb{R}^2|xy\ge0, x\ne-1\}$
Work Step by Step
The denominator cannot be equal to 0. Therefore, $x\ne-1$. Moreover, the values under the square root must be greater than or equal to 0, which means $xy\ge0$.
$D=\{(x,y)\in\mathbb{R}^2|xy\ge0, x\ne-1\}$
