Easy question on differentiation

Hi I have a really easy question that I do not understand here.

y = (2sqrt(x))/(1-x)),

and for dy/dx I got (x+1)/(sqrt(x)(1-x)^2)

Here's what I'm confused about,

For what values of x is dy/dx zero.

My answer will be -1 since if the numerator is zero, dy/dx will be zero but the answer says never..

Thank you for your help!!

Re: Easy question on differentiation

Notice that the domain of your derivative is $\displaystyle \displaystyle \begin{align*} x \in \mathbf{Z} ^{+} \backslash \{ 1 \} \end{align*}$

Re: Easy question on differentiation

How did you know that the domain of this derivative is as such?

Thank you!

Re: Easy question on differentiation

Square roots are only defined for nonnegative values, and denominators can't ever be 0.