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
原创 | 2022-10-10 16:04:57 |浏览:1.6万
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