It depends on what you're given. The parts of a parabola are:
vertex (h,k), p = directed distance for the vertex to the focus, which
is also the directed distance from the directrix line to the vertex.
If it opens upward or downward the standard equation is
{x - h)² = 4p(y - k), upward if p is positive, downward if p is negative.
If it opens rightward or leftward the standard equation is
{y - k)² = 4p(x - k), rightward if p is positive, leftward if p is negative.
Post a problem with some of those given and we'll show you how.
Edwin
