3. What is the x-coordinate of the vertex of y = 2 (x + 8) (x - 10) ?

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.