Part A)
The equation of the directrix is x=-5+8=3, x=3
Part B)
After using 'Perpendicular line' tool and 'Intersect' tool, we obtain the purple line and point A. A=(3,2)
The vertex V has to be on the axis of symmetry, halfway between points A and F. Vertex is V=(-1,2)
Part 3)
The focus is to the left of the vertex; therefore, the parabola opens to the left.
In general,

Then, in our case,

Thus, p=-4
Finding the equation in vertex form,

The answer is x=-(y-2)^2/16-1