Answer
$y^2=-24x$
Work Step by Step
We are told that the focus is to the left of the given vertex; thus, $ p$ is the negative of the distance between the two points.
So, $p=-6$
Since the vertex and focus have the same x-coordinate, the parabola must have a vertical axis.
Now, we will write the equation for the parabola that has a vertical axis using the vertex and $p$.
$y^2=4px \implies y^2=(4)(-6)x $
$\implies y^2=-24x$
