Answer
$x^2=- 12y$
Work Step by Step
Here, the focus is below the origin and the focus $(0,-3)$ refers to $p=-3$.
The standard form of a vertical parabola is given as: $x^2=4py$
when the parabola with vertical axis of symmetry.
Now, we will plug the value of $p=-3$ in the standard form of parabola to obtain:
$x^2 =(4)(-3) y \implies x^2=- 12y$
Hence, the required equation of the parabola is:
$x^2=- 12y$
