Find the center and radius of the circle x2+y2=16x^2 + y^2 = 16x2+y2=16.
Center: (0,0)(0,0)(0,0), Radius: 444
Center: (0,0)(0,0)(0,0), Radius: 161616
Center: (4,4)(4,4)(4,4), Radius: 444
Center: (4,0)(4,0)(4,0), Radius: 444