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if-lim-n-1-x-7n-29n-2023-find-x-




Question Number 196267 by Rodier97 last updated on 21/Aug/23
          if   lim_(n→+∞)  (1+ (x/(7n)))^(29n) =2023     find x ??
$$ \\ $$$$ \\ $$$$ \\ $$$$ \\ $$$$\:\:{if}\:\:\:{lim}_{{n}\rightarrow+\infty} \:\left(\mathrm{1}+\:\frac{{x}}{\mathrm{7}{n}}\right)^{\mathrm{29}{n}} =\mathrm{2023} \\ $$$$\:\:\:\boldsymbol{\mathrm{find}}\:\boldsymbol{{x}}\:?? \\ $$$$ \\ $$$$ \\ $$$$ \\ $$$$ \\ $$$$ \\ $$
Commented by mr W last updated on 21/Aug/23
find x?  but you said x→+∞
$${find}\:{x}? \\ $$$${but}\:{you}\:{said}\:{x}\rightarrow+\infty \\ $$
Commented by mr W last updated on 21/Aug/23
i guess you meant n→+∞
$${i}\:{guess}\:{you}\:{meant}\:{n}\rightarrow+\infty \\ $$
Answered by mr W last updated on 21/Aug/23
 lim_(n→+∞)  (1+ (x/(7n)))^(29n)    =lim_(n→+∞)  [(1+ (x/(7n)))^((7n)/x) ]^((29x)/7)    =lim_(m→+∞)  [(1+ (1/m))^m ]^((29x)/7)   with m=((7n)/x)  =e^((29x)/7) =2023  ⇒x=(7/(29))ln (2023)
$$\:\underset{{n}\rightarrow+\infty} {\mathrm{lim}}\:\left(\mathrm{1}+\:\frac{{x}}{\mathrm{7}{n}}\right)^{\mathrm{29}{n}} \\ $$$$\:=\underset{{n}\rightarrow+\infty} {\mathrm{lim}}\:\left[\left(\mathrm{1}+\:\frac{{x}}{\mathrm{7}{n}}\right)^{\frac{\mathrm{7}{n}}{{x}}} \right]^{\frac{\mathrm{29}{x}}{\mathrm{7}}} \\ $$$$\:=\underset{{m}\rightarrow+\infty} {\mathrm{lim}}\:\left[\left(\mathrm{1}+\:\frac{\mathrm{1}}{{m}}\right)^{{m}} \right]^{\frac{\mathrm{29}{x}}{\mathrm{7}}} \:\:{with}\:{m}=\frac{\mathrm{7}{n}}{{x}} \\ $$$$={e}^{\frac{\mathrm{29}{x}}{\mathrm{7}}} =\mathrm{2023} \\ $$$$\Rightarrow{x}=\frac{\mathrm{7}}{\mathrm{29}}\mathrm{ln}\:\left(\mathrm{2023}\right) \\ $$

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