Answer
$y=\sqrt{(1-\frac{1}{2}x)}$
Work Step by Step
First we graph:
$y=\sqrt{x}$
Next, we reflect and shift graph 2 units right:
$y=\sqrt{2-x}$
And finally, we stretch horizontally by 2:
$y=\sqrt{(1-\frac{1}{2}x)}$
See final graph.