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Question-207753




Question Number 207753 by efronzo1 last updated on 25/May/24
Answered by Berbere last updated on 25/May/24
A=Σ_(k=1) ^(2023) (1/(k(k+1)))=Σ_(k=1) ^(2023) ((k+1−k)/(k(k+1)))=Σ_(k=1) ^(2023) (1/k)−(1/(k+1))  =1−(1/(2024))=((2023)/(2024))  B=Σ_(k=0) ^(1011) (1/(1013+k))=Σ_(k=1) ^(2024) (1/k)−Σ_(k=1) ^(1012) (1/k)=H_(2024) −H_(1012)   (A/B)=((2023)/(2024(H_(2024) −H_(1012) )))
$${A}=\underset{{k}=\mathrm{1}} {\overset{\mathrm{2023}} {\sum}}\frac{\mathrm{1}}{{k}\left({k}+\mathrm{1}\right)}=\underset{{k}=\mathrm{1}} {\overset{\mathrm{2023}} {\sum}}\frac{{k}+\mathrm{1}−{k}}{{k}\left({k}+\mathrm{1}\right)}=\underset{{k}=\mathrm{1}} {\overset{\mathrm{2023}} {\sum}}\frac{\mathrm{1}}{{k}}−\frac{\mathrm{1}}{{k}+\mathrm{1}} \\ $$$$=\mathrm{1}−\frac{\mathrm{1}}{\mathrm{2024}}=\frac{\mathrm{2023}}{\mathrm{2024}} \\ $$$${B}=\underset{{k}=\mathrm{0}} {\overset{\mathrm{1011}} {\sum}}\frac{\mathrm{1}}{\mathrm{1013}+{k}}=\underset{{k}=\mathrm{1}} {\overset{\mathrm{2024}} {\sum}}\frac{\mathrm{1}}{{k}}−\underset{{k}=\mathrm{1}} {\overset{\mathrm{1012}} {\sum}}\frac{\mathrm{1}}{{k}}={H}_{\mathrm{2024}} −{H}_{\mathrm{1012}} \\ $$$$\frac{{A}}{{B}}=\frac{\mathrm{2023}}{\mathrm{2024}\left({H}_{\mathrm{2024}} −{H}_{\mathrm{1012}} \right)} \\ $$$$ \\ $$

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