The standard form of equation of parabola is (x-h)^2=4p(y-k) where the directrix is y=k-p and the vertex is as point (h,k). Thus given that the vertex is at (0,0) y=k-p the value of p will be: -4=0-p p=4 thus the equation will be: (x-0)^2=4*4(y-0) x^2=16y hence; y=1/16x^2 the answer is y=1/16x^2
