Question

Write the equation of a parabola with a vertex at (0, 0) and a directrix y = -1.

Answer 1

The equation is written:

$y = (x - h)^2 + k$
where h is the x coordinate of the vertex and k is the y coordinate of the vertex

So we just put it in the equation:

$y=x^2$

And thus if $y=-1$, then $x=i$, where $i= \sqrt{-1}$