Not sure what this is called, but basically trying to derive the actual derivative of the function $\displaystyle F(x)=3x^2 at (-2, 12)$

I would need to find $\displaystyle F(-2+h)$ which I got to as $\displaystyle 3h^2-12h+12$ and then plugging it into the slope formula. This is where I'm getting confused.

What I did:$\displaystyle M=((3h^2-12h+12)-12)/h$

Is that correct? I know the derivative is $\displaystyle 6x$ but I'm a little confused on getting to it on this question. Thanks!