Question 936635
the vertex form of a Parabola opening up(a>0) or down(a<0), 
{{{y=a(x-h)^2 +k}}} 
where(h,k) is the vertex  and  x = h  is the Line of Symmetry , 
the focus is (h,k + p), With Directrix y = (k - p), a = 1/(4p)
......
recommend starting with a sketch of the curve
Directrix is y=1, Length of latesrectum = 8, p = 2, a =1/(4p)= 1/8
v(0,-1)
{{{y = (1/8)x^2 -1}}}
{{{drawing(300,300,    -10,10,-10,10,    
 grid(1),
circle(0, -1,0.4),
circle(0, -3,0.4),
line(-4,-3,4,-3),

graph( 300, 300, -10,10,-10,10,0,1, -(1/8)x^2 - 1))}}}