X 2+Y 2 = 4x, the shift term is X 2+Y 2-4x = 0, and 4 is added to both sides of the equation, so X 2+Y 2-4x+4 = 4, that is, (X-2) 2+Y 2 = 4, indicating that the center of the circle is on 2,0. T = x 2+y 2, which means a circle with a center of 0,0 and a radius of T. If this circle needs to intersect with the previous circle with a minimum radius of 0 and a maximum diameter of the previous circle, then the minimum value of T is 0 and the maximum value is 4 2 =16.