Which is the standard form of the equation of a parabola with a focus of open paren 0 comma negative 3 close paren and its vertex at the origin?

A parabola with vertex at the origin and focus on the y-axis has equation x² = 4py, where p is the signed distance from the vertex to the focus. The focus (0, −3) gives p = −3, so x² = 4(−3)y = −12y. Therefore, the standard form is x squared equals negative 12 y, choice A.

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