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

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directrix y^2=-28x

directrix

y^{2} = - 28 x

x = 7

Solution steps

Rewrite

y^{2} = - 28 x

in the standard form:

4 (- 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

f (x) = x^{2} + x - 6

36 x^{2} + 5 y^{2} - 90 y - 495 = 0

\frac{x ^{2}}{9} + \frac{y ^{2}}{5} = 1

x^{2} + 9 y^{2} = 9

f (x) = x^{2} + 4 x - 12