The vertex is exactly half way between directrix and focus. In this case the vertex is (8,-7)
(h,k)
P is the distance between the vertex and either the directrix or focus, in this case p = 1.
a = 1/(4p) or 1/(4*1) or 1/4
write the equation in vertex form
y = a(x-h)^2 + k
y = 1/4(x-8)^2 -7
Answer:
4
Step-by-step explanation:

The answer is both all real numbers less than 0 and all real numbers greater than 0