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

The directrix y=-2x^2 is y= 1/8

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directrix y=-2x^2

directrix

y = - 2 x^{2}

y = \frac{1}{8}

Solution steps

Rewrite

y = - 2 x^{2}

in the standard form:

4 (- \frac{1}{8}) (y - 0) = (x - 0)^{2}

(h, k) = (0, 0), p = - \frac{1}{8}

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}{8})

Refine

y = \frac{1}{8}

y = 2 x^{2} - 3

(y + 1)^{2} = 16 (x - 3)

y = + x^{2} - 2 x + 5

y = 2 x^{2} - 7 x - 3

x^{2} + 5 x - 7