What is the limit of x^(1/x)x1x as x->oox?

1 Answer
Feb 24, 2017

Lt_(x->oo)x^(1/x)=1Ltxx1x=1

Explanation:

Let x^(1/x)=e^ax1x=ea, then taking natural log on both sides, we get

1/xlnx=a1xlnx=a and x^(1/x)=e^(lnx/x)x1x=elnxx

Hence, Lt_(x->oo)x^(1/x)=Lt_(x->oo)e^(lnx/x)Ltxx1x=Ltxelnxx

and as e^ueu is continuous Lt_(x->oo)x^(1/x)=e^(Lt_(x->oo)(lnx/x))Ltxx1x=eLtx(lnxx)

Now in Lt_(x->oo)e^(lnx/x)Ltxelnxx as x->oox, both numerator and denominators tend to infinity,

therefore we can apply L'Hospital's Rule and

Lt_(x->oo)(lnx/x)=Lt_(x->oo)((1/x)/1)=Lt_(x->oo)1/x=0Ltx(lnxx)=Ltx(1x1)=Ltx1x=0

Hence Lt_(x->oo)x^(1/x)=e^0=1Ltxx1x=e0=1