f(-x)=-x/(2^-x-1)+(-x)/2
=-x[1/(2^-x-1)+1/2]
=-x[2^x/(1-2^x)+1/2]
=x[2^x(2^x-1)-1/2]
=x[(2^x-1+1)/(2^x-1)-1/2]
=x[1+1/(2^x-1)-1/2]
=x[(1/(2^x-1)+1/2]
=x/(2^x-1)+x/2=f(x)
所以f(x)为偶函数
偶函数