SOLUTION: How do you determine the focus and directrix from the vertex formula y-k=a(x-h)^2 ?

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Question 358067: How do you determine the focus and directrix from the vertex formula
y-k=a(x-h)^2 ?
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
a = 1/(4p) ___ where p is the distance from the vertex to the focus (which are both on the axis of symmetry)

p is also the distance from the directrix to the vertex (the directrix is perpendicular to the axis of symmetry)