c.
tam giac A(1; 3); B(3; 1); C(-3; -3).
duong tron ngoai tiêp
M td AC ; M(-1;0)
AC (2;3)
trung truc AC : 2(x+1)+3y=2x+3y+3=0
N td BC ; N(0:-1)
BC(3;2)
trtrucBC. 3x+2y+2=0
I nghiêm
2x+3y+3=0
3x+2y+2=0
i(0;-1)
AI=căn(17)
(C): x^2+(y+1)^2=17