Cho B=1/12+1/13+…+1/22 Chứng minh B>1/2

Question

Cho B=1/12+1/13+…+1/22 Chứng minh B>1/2

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Aaliyah 1 năm 2021-09-07T08:02:02+00:00 2 Answers 10 views 0

Answers ( )

  1. lanhuong
    0
    2021-09-07T08:03:07+00:00
    Reply

    `B = 1/12 + 1/13+1/14+…+1/22`

    `⇒ B > 1/22 + 1/22 + 1/22 + … + 1/22`

    `⇒ B > 11/22 = 1/2`

    `⇒ B > 1/2` `(đpcm)`

    Vậy…

     

  3. minhnguyet
    0
    2021-09-07T08:03:42+00:00
    Reply

    B = ` 1 / 12 ` + `  1 / 13 ` + … +  ` 1 / 22 `

    B > ` 1 / 22 ` + `1 / 22 ` + …. + ` 1 / 22 ` 

    B > ` 187 / 22 ` 

    B > ` 187 / 22 ` > ` 1 / 2 ` = ` 11 / 22 `

    Vậy ` B ` > ` 1 / 2 `

    Chúc bạn học tốt !

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