How to do it and answer

(0,0)

Step-by-step explanation:

Let's put this in standard form in our minds.

Standard form of a circle is (x-h)^2 + (y-k)^2 = r^2.

(h,k) is the center, and r is the radius.

x^2 + y^2 = 121

(x-0)^2 + (y-0)^2 = 121

We can just think about this like they have a secret 0 as the h and k! The center is just (0,0). Good luck in your math class:)