lim(x->∝)(1/x)ln(x+e^x)
=lim(x->∝)ln(x+e^x) /x
=lim(x->∝)(1+e^x)/(x+e^x)
=lim(x->∝)e^x/(1+e^x)
=1
lim(x->∝)(x+e^x)^(1/x)=lim(x->∝)e^[ln(x+e^x)^(1/x)]=elim(x->∝)(1+e^x)/(x+e^x) =lim(x->∝)e^x/(1+e^x) 这两步是怎么得出来得呀罗必塔法则x->∝, 1+e^x->∝x+e^x->∝