X=1/16y^2 the directrix of the parabola is

To solve this problem you must apply the proccedure shown below:

 1. You have the following equation of a parabola, given in the problem above:

 x=1/16y^2

 2. Then, based on the graph attached, you have:

 p=y^2/4x
 p=8^2/(4)(4)
 p=64/16
 p=4

 3. The directrix is:

 directrix=h-p
 directrix=0-4
 directrix=-4

 The answer is:-4