Answer
$x^{2}= -24 y$
Work Step by Step
The equation of the directrix is y= 6. This equation is of the form $y= +a$
which corresponds to a parabola opening downwards with a=6.
The general form of the equation of a parabola which opens downwards is
$x^{2}= -4ay$
Then, the equation of the given parabola is
$x^{2}= -4\times6\times y$
or $x^{2}= -24 y$
