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

The directrix x^2-2x-9 is y=-41/4

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directrix x^2-2x-9

directrix

x^{2} - 2 x - 9

y = - \frac{41}{4}

Solution steps

Rewrite

y = x^{2} - 2 x - 9

in the standard form

4 \cdot \frac{1}{4} (y - (- 10)) = (x - 1)^{2}

(h, k) = (1, - 10), 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, - 10)

y-coordinate

y = - 10 - p

y = - 10 - \frac{1}{4}

Refine

y = - \frac{41}{4}

y = x^{2} - 8

- 0.4 x^{2} - 5

x + 5 + (y - 3)^{2} = 0

(x + 2)^{2} = 8 (y - 3)

\frac{x ^{4} - x ^{2} - 2 x - 1}{x ^{2} - x - 1}