Answer:
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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
8 + 3b= -13
-8. -8
3b= -21
Divide by 3
B= -7
