lim_(x->+oo) (x)^2 (e^(1/(x))-e^(1/(x+1))) ?

lim_(x->+oo) color(white)(..)(x)^2 (e^(1/(x))-e^(1/(x+1))) ?

1 Answer
Feb 25, 2018

lim_(x->oo) x^2(e^(1/x)-e^(1/(x+1))) = 1

Explanation:

Here's a slightly quick and dirty method using the series for e^t:

Note that:

e^t = 1+t+t^2/2+t^3/6+...

So:

e^(1/x)-e^(1/(x+1)) = (1+1/x+1/(2x^2)+...)-(1+1/(x+1)+1/(2(x+1)^2)+...)

color(white)(e^(1/x)-e^(1/(x+1))) = 1/(x(x+1))+1/(O(x^3))

So:

lim_(x->oo) x^2(e^(1/x)-e^(1/(x+1))) = lim_(x->oo) (x^2/(x(x+1))+1/(O(x))) = 1

Tony BTony B