What is the directrix x^2-8x-240 ?

The directrix x^2-8x-240 is y=-1025/4

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directrix x^2-8x-240

directrix

x^{2} - 8 x - 240

y = - \frac{1025}{4}

Solution steps

Rewrite

y = x^{2} - 8 x - 240

in the standard form

4 \cdot \frac{1}{4} (y - (- 256)) = (x - 4)^{2}

(h, k) = (4, - 256), 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

(4, - 256)

y-coordinate

y = - 256 - p

y = - 256 - \frac{1}{4}

Refine

y = - \frac{1025}{4}

- 2 x^{2} - 4 x + 34

2 x^{2} - 5 x + 5

y = \frac{x ^{2} 5 x 8}{x 3}

(x + 5)^{2} = - 20 (y - 2)

x^{2} + 4 x - 3