tính giá trị của biểu thức sau: 2/3.2/4.+2/4.2/5+2/5.2/6+2/6.2/7+2/7.2/8+2/8.2/9

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tính giá trị của biểu thức sau: 2/3.2/4.+2/4.2/5+2/5.2/6+2/6.2/7+2/7.2/8+2/8.2/9

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Iris 3 tháng 2021-09-24T22:12:51+00:00 2 Answers 5 views 0

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    0
    2021-09-24T22:14:09+00:00

    Cho A=2/3.2/4.+2/4.2/5+2/5.2/6+2/6.2/7+2/7.2/8+2/8.2/9

    A=2.2/3.4+2.2/4.5+…+2.2/8.9

    1/4xA=1/3.4+1/4.5+…+1/8.9

    1/4xA=1/3-1/4+1/4-1/5+…+1/8-1/9

    1/4xA=1/3-1/9

    1/4xA=2/9

    A=2/9:1/4

    A=8/9

    Vậy 2/3.2/4.+2/4.2/5+2/5.2/6+2/6.2/7+2/7.2/8+2/8.2/9=8/9

    0
    2021-09-24T22:14:47+00:00

    `2/3. 2/4+2/4. 2/5+2/5. 2/6+2/6. 2/7+2/7. 2/8+2/8. 2/9`

    `=2.2/3.4+2.2/4.5+2.2/5.6+2.2/6.7+2.2/7.8+2.2/8.9`

    `=4/3.4+4/4.5+4/5.6+4/6.7+4/7.8+4/8.9`

    `=4(1/3.4+1/4.5+1/5.6+1/6.7+1/7.8+1/8.9)`

    `=4(1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9)`

    `=4(1/3-1/9)`

    `=4(3/9-1/9)`

    `=4. 2/9`

    `=8/9`

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