What is the directrix 4x^2-25 ?

The directrix 4x^2-25 is y=-401/16

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directrix 4x^2-25

directrix

4 x^{2} - 25

y = - \frac{401}{16}

Solution steps

Rewrite

y = 4 x^{2} - 25

in the standard form:

4 \cdot \frac{1}{16} (y - (- 25)) = (x - 0)^{2}

(h, k) = (0, - 25), p = \frac{1}{16}

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

(0, - 25)

y-coordinate

y = - 25 - p

y = - 25 - \frac{1}{16}

Refine

y = - \frac{401}{16}

y = - 6 x^{2} + 37 x + 13

x^{2} = - 24 y

y = - 9 x^{2} + 2

x^{2} - 12 x + 1

y = (2 x + 3)^{2}