Answer
$\text{$y$ is NOT a function of $x$.}$
Work Step by Step
For an equation to be a function: any input $x$ will yield only one output $y$
If $x=0$
$$y = \pm \sqrt{1-2(0)} = \pm \sqrt{1} = \pm 1$$
As there are two different outputs resulting from the same input, the equation isn't a function
