The vertex of this parabola is the midpoint of the focus (-2,4) and where the directrix intersects the axis of symmetry of the parabola (-2,6)
This parabola must open downwards due to the position of the directrix and has equation of the form:
where (h,k) is the vertex.
This implies that:
The value of p is the distance from the vertex to the focus:
We substitute all the values into the formula to get: