Answer
$D=\{(x,y)\in\mathbb{R}|x\ge 0, 4\ge4x^2+y^2\}$
Work Step by Step
The values under the square root must be greater than or equal to 0. Thus, we need values of x and y where $x\ge 0$ and $4\ge4x^2+y^2$.
$D=\{(x,y)\in\mathbb{R}|x\ge 0, 4\ge4x^2+y^2\}$.
In the image, the domain is the intersection of the two shaded regions.
