Question

Write an equation of a parabola that opens downward, has a vertex at the origin, and a focus at (0,-1)

Answer 1

since the vertex is at the origin, and it opens down, the general formula will be
\[4py=x^2\]
\(p\) is the distance between the vertex and the focus, which is \(1\)
since it opens down use \(p=-1\) and get
\[-4y=x^2\] that is all