What is the directrix y=-(0.009(x-220)^2-220) ?

The directrix y=-(0.009(x-220)^2-220) is y=247.77777…

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directrix y=-(0.009(x-220)^2-220)

directrix

y = 247.77777 \dots

Solution steps

Rewrite

y = - (0.009 (x - 220)^{2} - 220)

in the standard form

4 (- 27.77777 \dots) (y - 220) = (x - 220)^{2}

(h, k) = (220, 220), p = - 27.77777 \dots

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

(220, 220)

y-coordinate

y = 220 - p

y = 220 - (- 27.77777 \dots)

Refine

y = 247.77777 \dots

What is the directrix y=-(0.009(x-220)^2-220) ?
The directrix y=-(0.009(x-220)^2-220) is y=247.77777…