parabola focal width

Question

What is the focal width of the parabolic equation $y=x^2-8x-18$?

I have pretty much all of the other vital numbers (vertex is $(4,-34)$, focus $(4, -\frac{87} 4$)) but am having a problem figuring the focal width.

Answer 1

The focal width of the parabola $(x-h)^2=4p(y-k)$ is $|4p|$.

If you know the vertex, you must know how to transform it to this standard form $$(x-4)^2=y+34$$

So the focal width is $|4p|=1$.