令
m=(1+y)^y
lnm=ln(1+y)^y=yln(1+y) 两边求导得
1/m *m'=ln(1+y)+y/(1+y)
m'=m [ ln(1+y)+y/(1+y) ]
=(1+y)^y [ ln(1+y)+y/(1+y) ]谢谢大神