Determine all of the critical numbers of the given function.

I'm like 90% sure that means solve for x, check if what you got for x actually works, and that/those are your critical number(s).

Anyways, here's the problem:

$\displaystyle g(x) = x - \sqrt{14-x} - 2$

Any ideas anyone? I tried solving for x:

$\displaystyle 0 = x-\sqrt{14-x} - 2$

then

$\displaystyle \sqrt{14-x} = x-2$

then squared both sides

$\displaystyle 14-x = x^2-4$

then moved some stuff around

$\displaystyle 18 = x^2+x$

and now I'm stuck there, not even knowing if I'm supposed to be doing this.

HALP