Question

Plz help mid life problem here!!!!
Find the standard form of the equation of the parabola with the given characteristic(s) and the vertex at the origin.....??????the directrix is y=3

Answer 1

If the directrix is y = 3 and the vertex is (0,0) the parabola is concave downward and p =3. So the equation must be x^2=-12y

Answer 2

right but where does the -12y come from and how does one know that it is concave???? what is concave anyways???