Find the vertex focus and directrix of the parabola x 42 4
Find the vertex, focus, and directrix of the parabola, (x + 4)^2 = -4(y - 5) vertex (x, y) = -4, 5 focus (x, y) = directrix
Solution
(x + 4)2 = -4(y - 5)
this is of the form (x - h)2 = 4p(y - k)
so from the given parabola,
4p = - 4
so, p = -1
therefore this parabola is a downward facing parabola.
h,k = -4,5
so the directrix will be 1 unit above the vertex.
that is, directrix is at y = 6.
and the focus will be 1 unit below the vertex. So focus = (-4,4).
