Answer:
y = -9
Step-by-step explanation:
The directrix is at the same distance from the vertex as the focus but on the opposite side of the vertex.
x coordinate the same for a focus and a vertex (4) means the parabola opens up or down and the directrix is parallel to the x-axis.
y coordinate of the focus greater than y coordinate of the vertex means the parabola opens up and the directrix lays below the vertex.
-1-(-5) = - 1 + 5 = 4
so: - 5 - 4 = -9 is the y coordinate of points of the directrix
