What is the vertex of y=-(x-4)(x+4)?

1 Answer
Dec 12, 2015

Vertex: (0,16)

Explanation:

You are given the equation in a factor form. By setting both factors to zero you know the two roots.
x-4=0

x=4

x+4=0

x=-4

The vertex is always exactly in between those two points so you can find where x is

x=(-4+4)/2

x=0
You can see that if you graph the equation
graph{-(x-4)(x+4) [-57, 57, -28.5, 28.5]}

Now that you have x, just plug that into the equation and solve for y

y=-(0-4)(0+4)

y=-(-4)(4)

y=-(-16)

y=16

So the vertex is (0,16)