What is the directrix-x^2+8x-10 ?

The directrix-x^2+8x-10 is y= 25/4

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directrix-x^2+8x-10

directrix

- x^{2} + 8 x - 10

y = \frac{25}{4}

Solution steps

Rewrite

y = - x^{2} + 8 x - 10

in the standard form

4 (- \frac{1}{4}) (y - 6) = (x - 4)^{2}

(h, k) = (4, 6), 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, 6)

y-coordinate

y = 6 - p

y = 6 - (- \frac{1}{4})

Refine

y = \frac{25}{4}

y = - 4 x^{2} - 12 x - 8

x^{2} + 16 y = 0

y = 4 x^{2} - 24 x - 30

8 y = x^{2}

x^{2} = 24 (y - 8)