well, you know that the equation for a parabola with vertex at (0,0) directrix y = -p is
x^2 = 4py
Your parabola has been shifted so the vertex is at (-2,4), so you want
(x+2)^2 = 4p(y-4)
Your directrix is at y = 1, which is 3 units below the vertex, so p=3
(x+2)^2 = 12(y-4)
see the graph at
http://www.wolframalpha.com/input/?i=parabola+(x%2B2)%5E2+%3D+12(y-4)
Write the equation in standard form, given the following information.
vertex(-2,4), directrix y=1
1 answer
1 answer