Answer
\[{{x}^{2}}=-4py,\text{ if }p>0\]
Work Step by Step
\[\begin{align}
& \text{The equation of the standard parabola with its vertex at the } \\
& \text{origin that opens downward is:} \\
& \text{ }{{x}^{2}}=-4py,\text{ if }p>0 \\
\end{align}\]
