.定义在R上函数满足F(X)+F(X+1)+F(X+2)=0,X属于R,且F(1)=a,F(2)=b,F(3)=c,求F

F(2)+F(3)+F(4)=0
F(4)=-b-c
F(3)+F(4)+F(5)=0
F(5)=-c+b+c=b
F(4)+F(5)+F(6)=0
F(6)=b+c-b=c
F(7)=-b-c
F(8)=b+c-c=b
F(2)=b,F(3)=c F(4)=-b-c F(5)=b F(6)=c F(7)=-b-c F(8)=b
F(2)=F(5)=F(3n-1)=b
F(3)=F(6)=F(3n)=c
F(4)=F(7)=F(3n+1)=-b-c
F(2011）=F(3*670+1)=-b-c