Explanation:
The equation of a parabola in vertex form is given by f(x) = a(x - h)^2 + k, where (h, k) is the vertex of the parabola.
Comparing the given equation f(x) = 0.7(x+3.1)^2+11.19 with the vertex form, we can see that h = -3.1 and k = 11.19. Therefore, the vertex of the parabola is (-3.1, 11.19).
The x-coordinate of the vertex is simply the value of h, which is -3.1. So, the x-coordinate of the vertex is -3.1.