Respuesta :

circles have the equation (x-h)²+(y-k)²=r² with the center at (h,k) and radius r
so if you bring the equation into this form you can read everything off

x²+y²-4=0
x²+y²=4
(x-0)²+(y-0)²=2²

so the radius r=2
h=0,k=0 which means the center is at (0,0)
good job