Use the general form of the equation of a parabola, given by:
(x - h)² = 4p(y - k)
where (h,k) is the vertex of the parabola.
the vertex is half way in between the focus and the directrix:
the x coordinate of the vertex is the same of the focus, the y coordinate is:
y = (focus coordinate + directrix)/2 = (1/4 - 1/4)/2 = 0
then, the vertex of the parabola is:
(0,0)
p is the value of the distance in between the