a-2b+c=0 ①
2a+b-c=0 ②
(b+2)^2-(a+1)(c+3)=0 ③
1)+2)得：3a-b=0,得：b=3a
代入1）得：c=2b-a=5a
代入3式得：(3a+2)^2-(a+1)(5a+3)=0
9a^2+12a+4-5a^2-3a-5a-3=0
4a^2+4a+1=0
(2a+1)^2=0
a=-1/2
故b=-3/2,c=-5/2