cho a=1/2+1/3+1/4+…+1/108+1/109 va b= 108/1+107/2+106/3+…+2/101+1/108 tinh a/b 21/10/2021 Bởi Gianna cho a=1/2+1/3+1/4+…+1/108+1/109 va b= 108/1+107/2+106/3+…+2/101+1/108 tinh a/b
Mik sửa lại đề nhé bn! `B = 108/1 + 107/2 + 106/3 +…+ 2/107 + 1/108` `= 1 + (107/2 + 1) + (106/3 + 1)+…+ (2/107 + 1) + (1/108 + 1)` `= 1 + 109/2 + 109/3 +….+ 109/107 + 109/108` `= 109/109 + 109/2 + 109/3 +…+ 109/107 + 109/108` `= 109.(1/2 + 1/3 +….+ 1/107 + 1/108 + 1/109)` `⇒ A/B = (1/2 + 1/3 + 1/4 +…+ 1/108 + 1/109)/(109.(1/2 + 1/3 +….+ 1/107 + 1/108 + 1/109)` `= 1/109` Bình luận
Mik sửa lại đề nhé bn!
`B = 108/1 + 107/2 + 106/3 +…+ 2/107 + 1/108`
`= 1 + (107/2 + 1) + (106/3 + 1)+…+ (2/107 + 1) + (1/108 + 1)`
`= 1 + 109/2 + 109/3 +….+ 109/107 + 109/108`
`= 109/109 + 109/2 + 109/3 +…+ 109/107 + 109/108`
`= 109.(1/2 + 1/3 +….+ 1/107 + 1/108 + 1/109)`
`⇒ A/B = (1/2 + 1/3 + 1/4 +…+ 1/108 + 1/109)/(109.(1/2 + 1/3 +….+ 1/107 + 1/108 + 1/109)`
`= 1/109`
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