If the vertex of a parabola is (0,3), what is the axis of symmetry?

X=3, that would give you a vertical line through the point 0,3

The axis of symmetry would be x=0.

The axis of symmetry intersects directly through the vertex because the vertex is the midpoint of the parabola and the axis of symmetry is the line in which splits the portability into two symmetrical halves. Therefore, the axis of symmetry is the x-coordinate of the vertex where a line can be calculated that splits the pots ILS into two symmetrical halves.