What is the directrix (x-80)^2=-320(y-20) ?

The directrix (x-80)^2=-320(y-20) is y=100

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directrix (x-80)^2=-320(y-20)

directrix

y = 100

Solution steps

Rewrite

(x - 80)^{2} = - 320 (y - 20)

in the standard form:

4 (- 80) (y - 20) = (x - 80)^{2}

(h, k) = (80, 20), p = - 80

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

(80, 20)

y-coordinate

y = 20 - p

y = 20 - (- 80)

Refine

y = 100

What is the directrix (x-80)^2=-320(y-20) ?
The directrix (x-80)^2=-320(y-20) is y=100