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
