x≠0，设任意x1,x2∈{x|x≠0，x∈R}且x1f（x1）-f（x2）=x1+1/x1-x2+1/x2=x1x2+x2/x1x2-x1x2+x1/x1x2=x2-x1/x1x2当x10x1x2>0x2-x1/x1x2>0即f（x1）>f（x2）,所以该函数在定义域上是单调减函数当0当x1<00，x1x2<0，x2-x1/x1x2<0即f（x1）综上所述，当x1当0当x1<0
