Maybe the logarithms can help

Calculus Level 2

lim x 0 + e 2 x x x = ? \large \lim_{x\to0^+} \dfrac{e^{2x}}{x^x} = \, ?


The answer is 1.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Chew-Seong Cheong
Feb 17, 2017

L = lim x 0 + e 2 x x x = lim x 0 + exp ( ln ( e 2 x x x ) ) = exp ( lim x 0 + ln ( e 2 x x x ) ) = exp ( lim x 0 + ( 2 x x ln x ) ) = exp ( lim x 0 + ( x ln x ) ) = exp ( lim x 0 + ( ln x 1 x ) ) A / case, L’H o ˆ pital’s rule applies. = exp ( lim x 0 + ( 1 x 1 x 2 ) ) Differentiate up and down w.r.t. x = exp ( lim x 0 + x ) = e 0 = 1 \begin{aligned} L & = \lim_{x \to 0^+} \frac {e^{2x}}{x^x} \\ & = \lim_{x \to 0^+} \exp \left( \ln \left(\frac {e^{2x}}{x^x} \right) \right) \\ & = \exp \left(\lim_{x \to 0^+} \ln \left(\frac {e^{2x}}{x^x} \right) \right) \\ & = \exp \left(\lim_{x \to 0^+} \left(2x - x \ln x \right) \right) \\ & = \exp \left(\lim_{x \to 0^+} \left(- x \ln x \right) \right) \\ & = \exp \left(\lim_{x \to 0^+} \left(-{\color{#3D99F6}\frac{\ln x}{\frac 1x}} \right) \right) & \small \color{#3D99F6} \text{A }\infty/\infty \text{ case, L'Hôpital's rule applies.} \\ & = \exp \left(\lim_{x \to 0^+} \left({\color{#3D99F6}\frac{\frac 1x}{\frac 1{x^2}}} \right) \right) & \small \color{#3D99F6} \text{Differentiate up and down w.r.t. }x \\ & = \exp \left(\lim_{x \to 0^+} x \right) \\ & = e^0 = \boxed{1} \end{aligned}

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...