ab+c^2-1=0
(2b+4)b+cc=1
2bb+4b+2+cc=3
2(b+1)^2+c^2=3
b+1=1或－1
c＝1或－1
a+b+c=2b+4+b+c=3b+4+c
＝1＋3(b＋1)+c
a+b+c=5或3或-1或-3