right off we see the vertex is (2,-1). at x=2 the distance from vertex to focus and vertex to directix does not involve x when at the vertex.
very generally when it is set that any point distance from focus and directix are equal,
the equation is ((x-xf)2)/(yf-yd)=y-(yf+yd), a parabola.
yf=y focus coodinate
yd= y directix coordinate
two equations simultaneous
yd=-17/2 straight line horizopntal to x-axis