答案是
（5a-b-9c）/52
请写出详细解题过程
參考答案:f（64/147）=6f（2)-f(3)-2f(7)=a
f(81/112)=4f(3)-4f(2)-f(7)=b
f(1/84)=-2f(2)-f(3)-f(7)=c
next step:take f(2),f(3),f(7)as something unknown,like x y z
and we have three equations,so it is easy that we get the answer of f(2) that you have already konwn.
thank you.Bye.
