What is the directrix 3x^2-24x-15 ?

The directrix 3x^2-24x-15 is y=-757/12

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directrix 3x^2-24x-15

directrix

3 x^{2} - 24 x - 15

y = - \frac{757}{12}

Solution steps

Rewrite

y = 3 x^{2} - 24 x - 15

in the standard form

4 \cdot \frac{1}{12} (y - (- 63)) = (x - 4)^{2}

(h, k) = (4, - 63), p = \frac{1}{12}

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

(4, - 63)

y-coordinate

y = - 63 - p

y = - 63 - \frac{1}{12}

Refine

y = - \frac{757}{12}

(x + 4)^{2} = 12 y - 24

x^{2} - 2 x - 9

y = x^{2} - 8

- 0.4 x^{2} - 5

x + 5 + (y - 3)^{2} = 0