The equation for the circle below is x2 + y2 = 64. What is the length of the circle's radius?

First we write equation for circle that consist coordinates of the center and it consists radius. Equation goes like this:

(x-x1) ^2 + (y-y1) ^2 = r^2

x1 and y1 are coordinates of the center. since the circle's center is at coordinate start that means that (x1, y1) = (0,0)

that means that 64 on the right side of given equation is r^2

r^2 = 64

r = 8

Answer is 8