What is the directrix (y+1)^2=12x ?

The directrix (y+1)^2=12x is x=-3

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directrix (y+1)^2=12x

directrix

(y + 1)^{2} = 12 x

x = - 3

Solution steps

Rewrite

(y + 1)^{2} = 12 x

in the standard form:

4 \cdot 3 (x - 0) = (y - (- 1))^{2}

(h, k) = (0, - 1), p = 3

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, - 1)

x-coordinate

x = 0 - p

x = 0 - 3

Refine

x = - 3

(y - 2)^{2} = 40 (x - 2)

(x - 3)^{2} - 1

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

y = - 3 x^{2} + 5 x

x^{2} + 16 x + 8