Answer
$y^2=-12x$
Work Step by Step
We are given that the directrix is right of the origin; thus, $ p$ is the negative of the distance between the two points.
So, $p=-3$
Since the vertex and focus have the same y-coordinate, the parabola must have a horizontal axis.
Now, we will write the equation for a parabola that has a vertical axis using the vertex and $p$.
$y^2=4px \implies y^2=(4)(-3) \times y $
$\implies y^2=-12x$
