Question

Please help! What is the equation of the parabola, in vertex form, with focus at (2,-4) and directrix y = -6?

A. (x-2)^2=4(y+5)

B. (x-2)^2=-1/4(y+5)

C. (y+4)^2=-4(x-2)

D. (x+2)^2=1/4(y+4)

Answer 1

so the parabola equation in vertex form is like http://www.mathwarehouse.com/geometry/parabola/images/standard-vertex-forms-thumb.png

so we know the vertex, is at ( 2, -4 )
so we know the directrix location, that is y = -6

so keep in mind that the distance from the directrix to the vertex, is the same distance from the vertex to the focus

so