What is the directrix-x^2-4x ?

The directrix-x^2-4x is y= 17/4

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directrix-x^2-4x

directrix

- x^{2} - 4 x

y = \frac{17}{4}

Solution steps

Rewrite

y = - x^{2} - 4 x

in the standard form

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

(h, k) = (- 2, 4), p = - \frac{1}{4}

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

(- 2, 4)

y-coordinate

y = 4 - p

y = 4 - (- \frac{1}{4})

Refine

y = \frac{17}{4}

4 y^{2} - 12 y + 56 x + 177 = 0

3 x^{2} + 19 x - 40

(y - 10)^{2} = - 12 (x + 2)

x^{2} + 4 x - 8 y + 12 = 0

x^{(2)} - 6 x + 5 y = - 34