# What is the vertex form of #y= (3x+9)(x-2) #?

##### 1 Answer

Mar 12, 2017

#### Explanation:

First let's expand the equation:

which simplifies to:

Let's find our vertex using

We find the x value of our vertex to be

(

Plug it into our equation and find y to be

so our vertex is at

We can also check this with a graph:

graph{(3x^2+3x-18) [-10.3, 15.15, -22.4, -9.68]}

Now that we have our vertex, we can plug it into the vertex form!

where

so

In the end we find: