y=x/(x+1)同取对数:lny=lnx/(x+1)lny=lnx-ln(x+1)两边同时对x求导:y'/y=1/x-1/(x+1)y'=y/x(x+1)y'=x/(x+1)/x(x+1)y'=1/(x+1)^2有不懂欢迎追问
