Answer
False.
Work Step by Step
Incorrect application of the chain rule; $\dfrac{du}{dx}$ was not included in the solution.
Correct Solving:
$u=(1-x)$; $\dfrac{du}{dx}=-1$
$y=\sqrt{u};\dfrac{dy}{du}=\dfrac{1}{2\sqrt{u}}$
$\dfrac{dy}{dx}=\dfrac{dy}{du}\times\dfrac{du}{dx}=-\frac{1}{2}(1-x)^{-\frac{1}{2}}.$
