$\displaystyle f(x)=\displaystyle\sqrt{49-x^2}+7 \cos^{-1}\left(\frac{x}{7}\right)$

So that F'(x) has this format:

$\displaystyle \displaystyle -\left(\frac{x+c}{mx+n}\right)^{p}$

When I derive this, I get:

$\displaystyle \diplaystyle\frac{-x}{\sqrt{(49-x^2})}+\frac{1}{\sqrt{(1-(\frac{x}{7})^2)}}$

How do I get in into that format?