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Question-134758




Question Number 134758 by rs4089 last updated on 07/Mar/21
Commented by rs4089 last updated on 07/Mar/21
prove it
$${prove}\:{it} \\ $$
Answered by mnjuly1970 last updated on 07/Mar/21
Σ_(n=0) ^∞ (x^n /(n!)) is convergent .     lim _(n→[) (x^(n+1) /((n+1)!)) ÷(x^n /(n!))     =lim_(n→∞) (x/(n+1))=0  ∀x∈R         ∴lim_(n→∞) x^n .(1/(n!))=0
$$\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\frac{{x}^{{n}} }{{n}!}\:{is}\:{convergent}\:. \\ $$$$\:\:\:{lim}\:_{{n}\rightarrow\left[\right.} \frac{{x}^{{n}+\mathrm{1}} }{\left({n}+\mathrm{1}\right)!}\:\boldsymbol{\div}\frac{{x}^{{n}} }{{n}!} \\ $$$$\:\:\:={lim}_{{n}\rightarrow\infty} \frac{{x}}{{n}+\mathrm{1}}=\mathrm{0}\:\:\forall{x}\in\mathbb{R} \\ $$$$\:\:\:\:\:\:\:\therefore{lim}_{{n}\rightarrow\infty} {x}^{{n}} .\frac{\mathrm{1}}{{n}!}=\mathrm{0} \\ $$

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