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prove-lim-n-x-n-0-when-x-lt-1-




Question Number 197808 by mokys last updated on 29/Sep/23
prove lim_(n→∞)  x^n  = 0    when ∣x∣ < 1
$${prove}\:\underset{{n}\rightarrow\infty} {{lim}}\:{x}^{{n}} \:=\:\mathrm{0}\:\:\:\:{when}\:\mid{x}\mid\:<\:\mathrm{1} \\ $$
Commented by Noorzai last updated on 30/Sep/23
please give more information
$${please}\:{give}\:{more}\:{information}\: \\ $$
Answered by mr W last updated on 30/Sep/23
say ∣x∣=a with 0<a<1  1>a>a^2 >...a^n >a^(n+1) >...>0  ⇒lim_(n→∞) a^n =0  −a^n ≤x^n ≤a^n   lim_(n→∞) (−a^n )≤lim_(n→∞) x^n ≤lim_(n→∞) a^n   0≤lim_(n→∞) x^n ≤0  ⇒lim_(n→∞) x^n =0
$${say}\:\mid{x}\mid={a}\:{with}\:\mathrm{0}<{a}<\mathrm{1} \\ $$$$\mathrm{1}>{a}>{a}^{\mathrm{2}} >…{a}^{{n}} >{a}^{{n}+\mathrm{1}} >…>\mathrm{0} \\ $$$$\Rightarrow\underset{{n}\rightarrow\infty} {\mathrm{lim}}{a}^{{n}} =\mathrm{0} \\ $$$$−{a}^{{n}} \leqslant{x}^{{n}} \leqslant{a}^{{n}} \\ $$$$\underset{{n}\rightarrow\infty} {\mathrm{lim}}\left(−{a}^{{n}} \right)\leqslant\underset{{n}\rightarrow\infty} {\mathrm{lim}}{x}^{{n}} \leqslant\underset{{n}\rightarrow\infty} {\mathrm{lim}}{a}^{{n}} \\ $$$$\mathrm{0}\leqslant\underset{{n}\rightarrow\infty} {\mathrm{lim}}{x}^{{n}} \leqslant\mathrm{0} \\ $$$$\Rightarrow\underset{{n}\rightarrow\infty} {\mathrm{lim}}{x}^{{n}} =\mathrm{0} \\ $$
Commented by mokys last updated on 30/Sep/23
thank you
$${thank}\:{you}\: \\ $$

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