The x-coordinate of the vertex of this parabola would be -2.
You can find the x-coordinate of any parabola by using the formula -b/2a, in which a is the number attached to x^2 and b is the number attached to x.
In this case a = 3 (since it is attached to x^2) and b = 12 (because it is attached to x). So we can solve using these pieces of information.
-b/2a = x
-(12)/2(2) = x
-12/6 = x
-2 = x
