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Homework Help: Find equation of parabola with focus and directrix

  1. Mar 27, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the equation of the parabola with focus (0, -4) and directrix y = -2

    i barely understand this thing. i mean how do i find the vertex.
    the book says D1 = focus to any point on the graph, and D2= the point on the graph to the directrix. and D1 = D2. how do i graph if i dont know the vertex

    2. Relevant equations

    3. The attempt at a solution
    answer: y + 3 = -1/4(x)2
  2. jcsd
  3. Mar 28, 2010 #2
    The vertex is the midpoint between the focus and the directrix.
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