In each of the following, find the coordinates of the focus, axis of the parabola, the equation of the directrix and the length of the latus rectum.

x2 = – 9y


The given equation is x2 = -9y

Here, the coefficient of y is negative.


Hence, the parabola open downwards.


On comparing this equation with x2 = -4ay, we get,


-4a = -9


a =


Thus,


Co-ordinates of the focus = (0,-a) =


Since, the given equation involves x2, the axis of the parabola is the y-axis.


Equation of directrix, y = a, then,


x =


Length of latus rectum = 4a = 9


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