Question

Find the standard form of the equation of the parabola with a focus at (0, -10) and a directrix at y = 10.

How would I solve this?

Answer 1

Notice that the vertex is \((0,0)\) here because it is the midpoint between focus and directrix line.

Since the focus is below the directrix line, the parabola faces downwards :
\[y = -\frac{1}{4a}x^2\]

Answer 2

y=-(1/40)x^2?

Answer 3

where \(a\) is the distance between "focus" and "vertex"