Answer:

Step-by-step explanation:
We want to find the equation of the parabola with a focus of 
 and directrix 
.
Considering the directrix, the quadratic graph must open downwards.
The equation of this parabola is given by the formula,
, where 
 is the vertex of the parabola.
The axis of this parabola meets the directrix at 
.
Since the vertex is the midpoint of the focus and the point of intersection of the axis of the parabola and the directrix,
 and 
.
The equation of the parabola now becomes,
.
Also 
 is the distance between the vertex and the directrix.

This implies that 
.
Since the parabola turns downwards,
 
.
Our equation now becomes,
.
.
We make y the subject to get,
.
This is the same as 
.