How do you find the equation of the parabola when you have the vertex focus and directrix?

To find the equation of a parabola given the vertex, focus, and directrix, start by identifying the vertex coordinates ((h, k)), the focus ((h, k + p)) for a vertical parabola (or ((h + p, k)) for a horizontal one), and the distance (p) from the vertex to the focus. The directrix will be a line located at (y = k - p) for vertical parabolas or (x = h - p) for horizontal ones. The standard form of the equation is ((x - h)^2 = 4p(y - k)) for vertical parabolas and ((y - k)^2 = 4p(x - h)) for horizontal parabolas. Substitute (p) with the distance calculated from the vertex to the focus or directrix to finalize the equation.