Hey guys, this is likely a really simple problem I have here.

basically my problem is to find the derivative of $\displaystyle \frac {-18}{(x^2 - 9)^2} $

So I make that $\displaystyle (-18)(x^2 - 9)^-2 $ so I can use the product rule.

So the derivative of $\displaystyle (x^2 - 9)^ -2) $ is $\displaystyle \frac {2x}{(x^2 - 9)^2} $

I do not know how to find the derivative of -18. I need this derivative to use the product rule, right? I believe it to be 0 or 1... but I have no idea. Please help!