Question

what is the equation of the axis of symmetry?

Explanation:

Step1: Identify parabola vertex x-coordinate

The vertex of the parabola is at $(0, -9)$, so its x-coordinate is $0$.

Step2: Axis of symmetry formula

For a vertical parabola, the axis of symmetry is the vertical line through the vertex, given by $x = \text{vertex x-coordinate}$.

Answer:

$x=0$