# What is the vertex of # y= x^2 -9 - 8x#?

##### 2 Answers

The vertex is

#### Explanation:

First place the equation in standard form.

This is a quadratic equation in standard form,

The vertex is the maximum or minimum point of a parabola. In this case, since

To find the vertex of a parabola in standard form, first find the axis of symmetry, which will give us

Axis of Symmetry

Substitute the values for

Simplify.

Determine the value for

Substitute

Simplify.

Simplify.

Vertex =

graph{y=x^2-8x-9 [-10.21, 7.01, -26.63, -18.02]}

#### Explanation:

We are given

First I want to get this into standard form This is easy, we just need to reorder it to fit the

Now we have

Now we plug in

Well, let's take a look at that:

After we did all this work, let's make

Now we've got

Now this is in vertex form, and once we have that it's very quick to find the vertex. This is vertex form,

In the case of our equation we have

*PLEASE NOTE* that

example:

So, the vertex is

graph{x^2-8x-9}

Looks like we got it right!! Nice job!