(y-7)^2 = 12x

Find the directrix

2 answers

49/12
no matter. the proposed answer is bogus. The directrix is a line, not just a number.

Recall that the parabola

y^2 = 4px

has directrix at x = -p.

Your parabola is shifted up, but that does not change the directrix. So, the desired line is clearly

x = -3

see the properties at

http://www.wolframalpha.com/input/?i=parabola+%28y-7%29^2+%3D+12x