Question

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

Answer 1

x = 1

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.