lim(ⅹ→+∞)(lnx)^1/x

令lnx=y,x=e^y ,当x→+∞,y→+∞。

原式=lim(y→+∞)y^e^-y

=lim(y→+∞)e^-ylne^y

=lim(y→+∞)ye^-y

=lim(y→+∞)(e^-y -ye^-y)

=0-lim(y→+∞)y/e^y=-lim(y→+∞)1/e^y

=0