设:t=(1-x)/x,得,X=1/(t+1).f(x)+f(1-x/x)=1+x,f[1/(t+1)]+f{[1-1/(t+1)]}/[1/(t+1)]=f[1/(t+1)]+f(t)=1+1/(t+1).当t=/(t+1)时,有f(t)+f(t)=1+1/(t+1).2f(t)=1+1/(t+1).f(t)=1/2+1/[2(t+1)].当t=x时,有,f(x)=1/2+1/[(x+1)].∴函数f(x)的表达式是f(x)=1/2+1/[(x+1)].