Question 732109
You could literally use the distance formula and derive the equation.  You would need the directrix along with the given focus.  The directrix is the line, y=1  [do you know why?]


A parabola is the set of points equally distant from ______________ and ____________.    The vertex is exactly between them.  [You should fill in those two blanks.]


A good picture or representative graph would help.  Maybe you can draw one, label some parts and points, and write the needed equation to start.  The point, any general point, on the parabola will be (x, y).  The coordinate for any fitting point on the directrix would be (x, 1).  You obviously have the focus coordinates of (-1, 3).  This all should be enough for you to derive the equation for this parabola, which is often well shown in most of the textbooks.