What is the directrix y=-2x^2+64x-90 ?

The directrix y=-2x^2+64x-90 is y= 3377/8

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directrix y=-2x^2+64x-90

directrix

y = - 2 x^{2} + 64 x - 90

y = \frac{3377}{8}

Solution steps

Rewrite

y = - 2 x^{2} + 64 x - 90

in the standard form

4 (- \frac{1}{8}) (y - 422) = (x - 16)^{2}

(h, k) = (16, 422), p = - \frac{1}{8}

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

(16, 422)

y-coordinate

y = 422 - p

y = 422 - (- \frac{1}{8})

Refine

y = \frac{3377}{8}

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

4 x^{2} - 6 x - 2

4 x^{2} + 16 x - 3

x = 2 y^{2} - 1 - (5 y - 6)

x^{2} - 2 x - 4 y + 13 = 0

What is the directrix y=-2x^2+64x-90 ?
The directrix y=-2x^2+64x-90 is y= 3377/8