a+b/2=c.(1)
a/2-b-c=1.(2)
3a+b=-2.(3)
(1)-(2):
a/2+3b/2+c=c-1
a+3b=-2.(4)
由(3)(4)解得:
a=b=-1/2
则c=a+b/2=-3/4
(a,b,c)=(-0.5,-0.5,-0.75)
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