函数f(x)=lnx+1/e^x
f'(x)=1/x-e^(-x) (x>0)
g(x)=x[1/x-e^(-x)]
=1-x/e^x
g'(x)=-(e^x-xe^x)/e^(2x)
=(x-1)/e^x
g'(x)>0解得x>1,g'(x)