Answer:
-4y = x², or y = - x²/4, or y = -(1/4)x²
Explanation:
Because the focus is beneath the directrix, this vertical parabola opens down. The general formula is 4py = x².
Because the distance between focus and directrix is 2 units, p = -1 here. The negative sign shows that the parabola opens down.
4py = x² becomes 4(-1)y = x², or -4y = x², or y = - x²/4