Answer:
The x-intercepts of a quadratic function are the points where the graph of the function intersects the x-axis. If a quadratic function has x-intercepts at (-3, 0) and (3, 0), then the graph of the function is symmetric with respect to the y-axis.
The line of symmetry of a symmetric function is a vertical line that passes through the vertex of the function. In this case, the vertex of the function is located at the midpoint of the x-intercepts, which is at the point (0,0). Therefore, the equation of the line of symmetry is simply the equation of the vertical line passing through (0,0), which is:
x = 0
So the equation of the line of symmetry is x = 0.