Question 297166
Cursing is not allowed on this site.  

We first need to find the value of x using x = -b/2a.

In your trinomial, a = 1, b = -3 and c = -21.  See it?

We now use a = 1 and b = -3 to find your x value.

x = -(-3)/2(1)

x = 3/2

Now, x = 3/2 is the value of the x-coordinate of your vertex point in the form (x,y).

Understand?

I found x but how do I find y?

Simply replace every x that you see in your trinomial with 3/2 and simplify.

I will set it up and you do the math.

y = (3/2)^2 - 3(3/2) - 21

When you solve for y, you will then have your vertex point in the form (x,y).

Understand?