What is the directrix y=-x^2-1 ?

The directrix y=-x^2-1 is y=-3/4

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directrix y=-x^2-1

directrix

y = - x^{2} - 1

y = - \frac{3}{4}

Solution steps

Rewrite

y = - x^{2} - 1

in the standard form:

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

(h, k) = (0, - 1), p = - \frac{1}{4}

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, - 1)

y-coordinate

y = - 1 - p

y = - 1 - (- \frac{1}{4})

Refine

y = - \frac{3}{4}

+ 6 x^{2} + 6 x - 12

y^{2} = 20 (x - 10)

y = 3 x^{2} - 18 x + 23

y^{2} - 5 x + 12 y = - 16

3 y^{2} = 10 x