Saturday 13 June 2015

calculus - Infinity indeterminate form that L'Hopital's Rule: $lim_{xto0^+}frac{e^{-frac{1}{x}}}{x^{2}}$



When I tried to find the limit of
$$
\lim_{x\to0^+}\frac{e^{-\frac{1}{x}}}{x^{2}}
$$

by applying L'Hopital's Rule the order of denominator would increase. What else can I do for it?


Answer



Let $ y = \dfrac{1}{x}$, then $x = \dfrac{1}{y} \Rightarrow L = \displaystyle \lim_{y \to +\infty} \dfrac{y^2}{e^y}= \displaystyle \lim_{y \to +\infty} \dfrac{2y}{e^y}=\displaystyle \lim_{y \to +\infty} \dfrac{2}{e^y}= 0$


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