(X-a)^2+y^2=r^2。 Substitute (0,0) (-1,1) into:

a^2=r^2,a=r

(a+ 1)^2+ 1=r^2,a^2+2a+2=r^2.

a=- 1，r= 1

C:(X+ 1)^2+Y^2= 1

2. Circle D passes through the point, and when P is at the point, AB=0.

When p is at (2,2), AB is maximum: omitted.