The vertex of the parabola is at (0,0), and the focus is at (0,-7).
The focus is given by the following values:

h and k represent the x and y values of the vertex. We want to solve for p.
Set the y value for the focus equal to -7:

We know that k = 0, so we can simplify to get p by itself:

Standard form of a vertical parabola is given by the following formula:

Plug in all of your known values into the formula:



The answer is
"y^2 = -28x".