Given equation of directrix : y = 3
• y - 3 = 0
Above equation is of the form, y - a = 0
Focus of the parabola F(0,-3) is of the form F(0,-a)
Therefore, a = 3
For directrix with equation y - a=0 and focus (0,-a), equation of the parabola is,
x2 = - 4ay
• x2 = - 12y