Tính`A=(1/2+1/3+1/4+….+1/19+1/20)/(19/1+18/2+17/3+…+2/18+1/19)`

Question

Tính`A=(1/2+1/3+1/4+….+1/19+1/20)/(19/1+18/2+17/3+…+2/18+1/19)`

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Jezebel 5 years 2021-05-20T23:43:41+00:00 2 Answers 47 views 0

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  1. Eirian
    0
    2021-05-20T23:45:18+00:00
    Reply

    Đáp án:

     

    Giải thích các bước giải:

     

    tinh-a-1-2-1-3-1-4-1-19-1-20-19-1-18-2-17-3-2-18-1-19

  2. ngockhue
    0
    2021-05-20T23:45:22+00:00
    Reply

    Đáp án+Giải thích các bước giải:

    $A=\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+…+\dfrac{1}{20}}{\dfrac{19}{1}+\dfrac{18}{2}+\dfrac{17}{3}+…+\dfrac{1}{19}}\\=\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+…+\dfrac{1}{20}}{1+\left(\dfrac{18}{2}+1\right)+\left(\dfrac{17}{3}+1\right)+…+\left(\dfrac{1}{19}+1\right)}\\=\\\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+..+\dfrac{1}{20}}{1+\dfrac{20}{2}+\dfrac{20}{3}+…+\dfrac{20}{19}}\\=\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+..+\dfrac{1}{20}}{20.\left(\dfrac{1}{2}+\dfrac{1}{3}+…+\dfrac{1}{19}+\dfrac{1}{20}\right)}\\=\dfrac{1}{20}$ 

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