What is the directrix y=-9x^2 ?

The directrix y=-9x^2 is y= 1/36

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directrix y=-9x^2

directrix

y = - 9 x^{2}

y = \frac{1}{36}

Solution steps

Rewrite

y = - 9 x^{2}

in the standard form:

4 (- \frac{1}{36}) (y - 0) = (x - 0)^{2}

(h, k) = (0, 0), p = - \frac{1}{36}

Parabola is symmetric around the y-axis and so the directrix is a line parallel to the x-axis, a distance

- p

from the center

(0, 0)

y-coordinate

y = 0 - p

y = 0 - (- \frac{1}{36})

Refine

y = \frac{1}{36}

y - 2 = 3 (x - 5)^{2}

y = (x - 12)^{2}

x \leq y^{2}

y^{2} = x - 3

y = x^{2} - 4 x - 4