Equation of the parabola with the vertex (0,3), axis parallel to OX, passing through (4,9)

Answer 1

x = a(y-3)^2 + 0
but (4,9) lies on it, so
4 = a(9-3)^2 + 0
4 = 36a
a = 1/9

x = (1/9)(y-3)^2 is your equation.