7/2+7/6+7/12+…+7/9900

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7/2+7/6+7/12+…+7/9900

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Lệ Thu 5 years 2021-05-19T16:36:34+00:00 1 Answers 19 views 0

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    2021-05-19T16:37:48+00:00

    Đáp án:

     `693/100`

    Giải thích các bước giải:

    `7/2+7/6+7/12+…+7/9900`

    `=7/1.2+7/2.3+7/3.4+…+7/99.100`

    `=7[1-1/2+1/2-1/3+1/3-1/4+…+1/99-1/100]`

    `=7[1-(1/2-1/2+1/3-1/3+1/4-…-1/99+1/100)]`

    `=7[1-1/100]`

    `=7*99/100`

    `=693/100`

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )