Answer:
x = 1
Step-by-step explanation:
The x-intercepts of the graph are the values of x where the factors are zero:
x = -8
x = 10
These are located symmetrically about the (vertical) line of symmetry, which passes through the vertex. In other words, the average of these two values of x is the x-coordinate of the vertex:
(-8 +10)/2 = 2/2 = 1
The x-coordinate of the vertex is x=1.
