tính: A=1.98+2.97+3.96+…+98.1/1.2+2.3+3.4+…+98.99

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tính: A=1.98+2.97+3.96+…+98.1/1.2+2.3+3.4+…+98.99

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Thanh Thu 5 years 2021-05-07T21:27:55+00:00 1 Answers 106 views 0

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  1. kiet
    0
    2021-05-07T21:29:47+00:00
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    Đặt `B=1*2+2*3+3*4+…+98*99=(98*99*100)/3`

    `A=[2(100-1)+3(100-2)+…+98(100-99)]/B`

    `A=[100(1+2+3+…+98)-B]/B`

    `A=[100(1+…+98)]/B-1`

    `A=(100*99*98/2)/B-1`

    `A=[100*99*98/2]/[99*98*100/3]-1`

    `A=(1/2)/(1/3)-1`

    `A=1/2`

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