Question

What is the vertex of y=(x+2)(x-2)

Answer 1

Answer is -4
The vertex will be the y value when x is 0, since 0 is the average number of the roots of this quadratic.
Then, you get (0+2)(0-2)=2*-2=-4

Answer 2

If we write the quadratic equation in the vertex form, will be easy to find the vertex.

The vertex form of a quadratic function is:

y = a(x - h)² + k

Where the vertex is (h. k).

We have:

y=(x+2)(x-2)

y = x² - 4

Form this we conclude: a = 1, h = 0, k = -4. Then:

A/ The vertex of y is (0, -4)