x＝0时，y=1x≠0时，y=(x+1+1/x)/(x+1/x)设x+1/x=t (t≥2，t≤-2)则y=(1+t)/t=1+1/t则1<1+1/t≤3/2,或1/2≤1+1/t<1综上以值域为[1/2，3/2]
