Answer:
6
Step-by-step explanation:
If the graph intersects the x-axis, then there is an x-intercept at that point. So, we know that 3 and 9 are the x-intercepts of the parabola.
Parabolas can only have 0, 1, or 2, x intercepts. The x coordinate of the vertex will be the average of the x coordinates of the x-intercepts, since the vertex will be in the middle of the 2 x intercept points.
Take the average of 3 and 9:
(3 + 9) / 2
12 / 2
= 6
The x coordinate of the vertex is 6.
