Trouble finding the derivative of $\frac{4}{\sqrt{1-x}}$ I've been trying to figure out how to differentiate this expression, apparently I don't know my differentiation rules as much as I thought. I've been trying to use Wolfram Alpha as a guide but I'm at a loss.
I need to differentiate $$\frac{4}{\sqrt{1-x}}$$
I first pull out the four so the problem becomes: $$4 * \frac{1}{\sqrt{1-x}}$$
I'm not sure what to do next, do I use the quotient rule? Wolfram alpha is giving me some crazy answers, I would appreciate it if someone could walk me through this step by step. Thanks.

A bit more detail than you asked for, but I hope it makes the problem clear:
When you differentiate $(f(x))^r$ you end up with $rf(x)^{r-1}f'(x)$. To see why, work through the following:
$$y=f(x)^r\\
\ln(y)=r\ln(f(x))$$
Now differentiate both sides:
$$(1/y)\frac{dy}{dx}=\frac{r}{f(x)}f'(x)$$
So $\frac{dy}{dx}=\frac{ry}{f(x)}f'(x)=rf'(x)f(x)^{r-1}$ when you substitute the expression for $y$ back in.
So your question comes down to : $4\frac{d}{dx}(1-x)^{-1/2}=4(-1/2)(1-x)^{-3/2}(-1)=\frac{2}{(1-x)^{3/2}}$.
