C(a,b)
L:x+3y-26=0,k(L)=-1/3
k(CB)=-1/k(L)
(b-6)/(a-8)=3
3a-b-18=0.(1)
AB的中点M(3,1)
k(CM)*k(AB)=-1
[(b-1)/(a-3)]*[(6+4)/(8+2)]=-1
a+b-4=0.(2)
(1),(2):
a=5.5,b=-1.5
C(5.5,-1.5)
r^2=62.5
(x-5.5)^2+(y+1.5)^2=62.5辛苦了，算这么多