Question 840633

Starting from {{{x^2=4py}}}, get {{{y=(1/(4p))x^2}}}, and because vertex is above the focus, {{{p=-(1/4)}}}.  Apply p in the equation and you have {{{y=(1/(4(-1/4)))x^2}}}, or {{{y=-x^2}}}.


Looking again that vertex is at (0,0), you can be sure that this parabola is {{{highlight(y=-x^2)}}}.


Check your book's discussion on deriving the parabola equation or also check http://en.wikipedia.org/wiki/Parabola