; Eq := (x,y) -> (x^2+y^2)*a + x*b + c*y + d = 0; Eq(-4,5); Eq(-2,7); Eq(4,-3); solve({Eq(-4,5),Eq(-2,7),Eq(4,-3)},{a,b,c,d}); C := subs({b = -2*a, c = -4*a, d = -29*a},Eq(x,y)); C := simplify(subs(a=1,C)); Cir := expand( (x-x0)^2 + (y-y0)^2 - R^2 = 0); solve(R^2-5=29,R);