College Algebra Question, PLEASE help Test Tomorrow!!?

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Hernandez1313

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find an equation of the parabola with directrix y = 2 and focus (0,-2)

the answer i got is y = 8x^2 but i worked it again and got y = 4x^2
 
The vertex is (0,0), 2 units from the focus, 2 units from the directrix.
p = 2, parabola opens down

-4py = x^2

-8y = x^2 or y = -(1/8)x^2 is the equation

If vertex had been somewhere else, (h,k), equation is
4p(y - k) = (x - h)^2 There is a neg sign if it opens down(focus below vertex).
If the parabola opens left or right, the equation is
4p(x - h) = (y - k)^2 If it opens left, focus to left of vertex, there is a neg
 
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