What is the directrix y^2-28x=0 ?

The directrix y^2-28x=0 is x=-7

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directrix y^2-28x=0

directrix

y^{2} - 28 x = 0

x = - 7

Solution steps

Rewrite

y^{2} - 28 x = 0

in the standard form:

4 \cdot 7 (x - 0) = (y - 0)^{2}

(h, k) = (0, 0), p = 7

Parabola is symmetric around the x-axis and so the directrix is a line parallel to the y-axis, a distance

- p

from the center

(0, 0)

x-coordinate

x = 0 - p

x = 0 - 7

Refine

x = - 7

3 y^{2} = - 4 x

(x + 3)^{2} = 4 (y - 1)

y = x^{2} - 4 x - 3

y = - x^{2} + 6 x

y = x^{2} - 4 x + 5