# How would you find the center and radius of #x^2 + y^2 - 81 = 0#?

##### 1 Answer

Dec 21, 2015

Center :

#### Explanation:

First, you put the 81 at the right side, you're now dealing with

You now recognize the square of the norm!

It means that the distance between the origin and any point of the circle has to be equal to 9, you have to see