# How do you solve #x^2 - 18x + 81 = 0# graphically?

##### 1 Answer

The vertex is

#### Explanation:

We begin with

Well, for vertex form, we could "complete the square". I'm a big fan of this method, but I always got to factoring *first*, and if that doesn't work I move on to other methods like completing the square or the quadratic formula.

So, let's begin with factoring.

We are trying to factor **multiplys** to **adds** to

So, the factors of

No, out of these factors we are supposed to have them add to

So,

There it is.

So, that means we can rewrite

No, look: there is no stretch factor for

To find other points, just replace

If we solve for when

Now you have the vertex and a couple of point to help guide you as you draw your graph

If you want to double check this, just graph it

graph{y=(x-9)^2+0}