求a、b、c 2=9a-3b+c -1=a-b+c 1=9a+3b+c
问题描述：
求a、b、c 2=9a-3b+c -1=a-b+c 1=9a+3b+c
答
2=9a-3b+c (1)
-1=a-b+c (2)
1=9a+3b+c (3)
(3)-(1)
-1=6b
b=-1/6
(1)+(3)
18a+2c=3 (4)
a+c=b-1=-7/6
2a+2c=-7/3 (5)
(4)-(5)
16a=16/3
a=1/3
c=-7/6-a=-3/2
所以a=1/3,b=-1/6,c=-3/2