Finding the Radius and Center of a Circle with x2+y2=16

[jessi tompkin]

Homework Statement

how do you find the radius and center with x2+y2=16 of a circle graph

Homework Equations

The Attempt at a Solution

I am completely stump don't even know where to start on this.

 

[statdad]

Do you know the standard form for the equation of a circle that has radius r?