I need this $\displaystyle \frac{-18477 s-2.82843\times 10^8}{s^2+15307 s+4.\times 10^8}$ to be in this format : $\displaystyle \frac{s+a}{(s+a)^2+w^2}$

I can easily factor the top to get the "s+a",

$\displaystyle -18477\frac{s+15307 }{s^2+15307s+4*10^8}$

Now $\displaystyle (s+15307)^2=s^2+30614 s+234304249$

but how can I factor the bottom in such a way to get the required form? Can someone help please?