令t=1/x ∵f(t)=t/(t+1) ∴f(x)=x/(x+1) ∵f(x)+f(1/x)=x/(x+1)+1/(x+1)=1 ∴F(1)+F(1/2)+F(2)+F(1/3)+F(3)+F(4)+F(1/4)=1/2+3=7/2