The given equation is x2 = –9y.
Here, the coefficient of y is negative. Hence, the parabola opens downwards.
On comparing this equation with x2 = –4ay, we obtain
- 4a = -9 ⇒ b = 9/4
∴Coordinates of the focus = (0, a ) =(0, - 9/4)
Since the given equation involves x2, the axis of the parabola is the y-axis.
Equation of directrix, y = a,i.c., y =9/4
Length of latus rectum = 4a = 9