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Question Number 152450 by fotosy2k last updated on 28/Aug/21

Commented by fotosy2k last updated on 28/Aug/21

pls help

$${pls}\:{help} \\ $$

Answered by JDamian last updated on 28/Aug/21

a_n =(1/3^n )+1+(1/n)   ∀ n∈N  a_n >1   ⇒  (B) and (D) are discarded    a_n  is decreasing  ∀n  ⇒ a_1  is the highest  a_1 =(1/3^1 )+1+(1/1)=(1/3)+2=(7/3)

$${a}_{{n}} =\frac{\mathrm{1}}{\mathrm{3}^{{n}} }+\mathrm{1}+\frac{\mathrm{1}}{{n}}\:\:\:\forall\:{n}\in\mathbb{N} \\ $$$${a}_{{n}} >\mathrm{1}\:\:\:\Rightarrow\:\:\left({B}\right)\:{and}\:\left({D}\right)\:{are}\:{discarded} \\ $$$$ \\ $$$${a}_{{n}} \:{is}\:{decreasing}\:\:\forall{n}\:\:\Rightarrow\:{a}_{\mathrm{1}} \:{is}\:{the}\:{highest} \\ $$$${a}_{\mathrm{1}} =\frac{\mathrm{1}}{\mathrm{3}^{\mathrm{1}} }+\mathrm{1}+\frac{\mathrm{1}}{\mathrm{1}}=\frac{\mathrm{1}}{\mathrm{3}}+\mathrm{2}=\frac{\mathrm{7}}{\mathrm{3}} \\ $$

Commented by fotosy2k last updated on 30/Aug/21

thank you

$${thank}\:{you} \\ $$

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