Answer:
Use the distance formula and the features with the definition of parabola unless you know the derived equation.
Directrix is the line on the other side of the focus from vertex. Directrix is x=8, for the general point (8,y). Parabola is the general point (x,y).
Distance from parabola to focus equals distance from parabola to directrix.
y2=-32X
x=1/x=y2
