The focus-directrix form of a parabola is (x - h)²<span> = 4p (y - k), where the </span>focus<span> is (h, k + p) and the directrix is y = k - p. in this case, h=0 k+p=5 k-p=-5 solve for p and k: (k+p)+(k-p)=5+(-5), 2k=0, k=0, p=5 </span>(x-0)²=4*5(y-0), x²=20y<span> so the standard form of a parabola is y=ax</span>²+bx+c <span>in this case, it is :y=(1/20)x</span>²