3) Passing the fixed point is independent of parameters. In this proposition, the parameter is a, if there is no a, it can only be A 0 = 1.

Therefore, x= 1/2 and f( 1/2)=2.

4) It has nothing to do with the fixed point, but (x+d/2) 2+(y+e/2) 2 = r 2 after the formula.

Make sure that R>0 is a circle and R=0 is a point.