Tính tổng sau: A= 2/1.4 + 2/4.7 + 2/7.10 +….+ 2/97.100

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Tính tổng sau:
A= 2/1.4 + 2/4.7 + 2/7.10 +….+ 2/97.100

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Parker 4 tháng 2021-08-23T07:24:01+00:00 2 Answers 19 views 0

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    0
    2021-08-23T07:25:16+00:00

    `A= 2/1.4 + 2/4.7 + 2/7.10 +…+2/97.100`

    `A : 2 = 1/1.4 + 1/4.7 + 1/7.10 +…+1/97.100`

    `A: 2 .3 = 3/1.4 + 3/4.7 + 3/7.10 +…+3/97.100`

    `A . 3/2 = 1/1 – 1/4 + 1/4- 1/7 +….+1/97-1/100`

    `A. 3/2 = 1 – 1/100`

    `A . 3/2 = 99/100`

    `A = 99/100: 3/2`

    `A= 99/100 . 2/3`

    `A= 33/50`

    Vậy `A= 33/50`

     

    0
    2021-08-23T07:25:32+00:00

    Đáp án:

     `A=33/50`

    Giải thích các bước giải:

     `A=2/1.4+2/4.7+2/7.10+…+2/97.100`

    `\to A=2/3.(3/1.4+3/4.7+3/7.10+…+3/97.100)`

    `\to A=2/3.(1-1/4+1/4-1/7+1/7-1/10+…+1/97-1/100)`

    `\to A=2/3.[1+(-1/4+1/4)+(-1/7+1/7)+(-1/10+1/10)+…+(-1/97+1/97)-1/100]`

    `\to A=2/3.(1+0+0+0+…+0-1/100)`

    `\to A=2/3.(1-1/100)`

    `\to A=2/3.(100-1)/100`

    `\to A=2/3.(99)/100`

    `\to A=33/50`

    Vậy `A=33/50`

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