What is the directrix y=x^2-2x-15 ?

The directrix y=x^2-2x-15 is y=-65/4

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directrix y=x^2-2x-15

directrix

y = x^{2} - 2 x - 15

y = - \frac{65}{4}

Solution steps

Rewrite

y = x^{2} - 2 x - 15

in the standard form

4 \cdot \frac{1}{4} (y - (- 16)) = (x - 1)^{2}

(h, k) = (1, - 16), 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

(1, - 16)

y-coordinate

y = - 16 - p

y = - 16 - \frac{1}{4}

Refine

y = - \frac{65}{4}

x^{2} - 10000 x - 24000000

y = - 3 x^{2} - 12 x - 17

3 x - 3 x^{2}

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

y^{2} = 36 x