Найти производную : Х-1/1+е^х

f(x)=(x-1)/(1+eˇx)f´(x)=(1.(1+eˇx)-(x-1).eˇx)/(1+eˇx)ˇ2==(1+eˇx-x.eˇx-eˇx)/(1+eˇx)ˇ2==(1-x.eˇx)/(1+eˇx)ˇ2