SOLUTION: Enter the Equation of the directrix X^2+16y=0

 

Hi

x^2+16y=0

y = (-1/16)x^2  V(0,0), Opening downward: -1/16 < 0

1/(4p) = -1/16

  p = -4

directrix is y = 4



the vertex form of a Parabola opening up(a>0) or down(a<0),  

where(h,k) is the vertex  and  x = h  is the Line of Symmetry

 a = 1/4p, where  the focus is (h,k + p)

With Directrix y = (k - p)