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

Find the derivative then make it into the format:

$\displaystyle

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

$

I got it to the form

$\displaystyle

\frac{-(x+7)}{\sqrt{49-x^2}}

$

Soooo shouldn't..

c=7

m=-1

n=49

p=1

Or have I done something wrong?