Làm giùm mình.

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Làm giùm mình.
lam-gium-minh

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Nick 5 years 2021-04-28T16:21:16+00:00 2 Answers 24 views 0

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  1. bonexptip
    0
    2021-04-28T16:22:20+00:00
    Reply

    A=$\frac{2^{2}}{3.5}$+$\frac{2^{2}}{5.7}$+$\frac{2^{2}}{7.9}$+…+$\frac{2^{2}}{21.23}$+$\frac{2^{2}}{23.25}$

    =2.($\frac{2}{3.5}$+$\frac{2}{5.7}$+$\frac{2}{7.9}$+…+$\frac{2}{21.23}$+$\frac{2}{23.25}$)

    =2.($\frac{1}{3}$-$\frac{1}{5}$+$\frac{1}{5}$-$\frac{1}{7}$+$\frac{1}{7}$-$\frac{1}{9}$+…+$\frac{1}{21}$-$\frac{1}{23}$+$\frac{1}{23}$-$\frac{1}{25}$

    =2.($\frac{1}{3}$-$\frac{1}{25}$)

    =2.($\frac{25}{75}$-$\frac{3}{75}$)

    =2.$\frac{22}{75}$

    =$\frac{44}{75}$

    -Team Legend of never die-

  2. sori
    0
    2021-04-28T16:23:01+00:00
    Reply

    Đáp án:

    $A = \frac{44}{75}$

    Giải thích các bước giải:

    $A = \frac{2²}{3.5} + \frac{2²}{5.7} + \frac{2²}{7.9}+…+ \frac{2²}{21.23} + \frac{2²}{23.25}$

    $A = 2(\frac{2}{3.5} + \frac{2}{5.7} + … + \frac{2}{21.23} + \frac{2}{23.25})$

    $A = 2(\frac{1}{3} – \frac{1}{5}+\frac{1}{5}- \frac{1}{7} + … + \frac{1}{21} – \frac{1}{23} + \frac{1}{23} – \frac{1}{25})$

    $A = 2(\frac{1}{3} – \frac{1}{25})$

    $A = 2.\frac{22}{75} $

    $A = \frac{44}{75}$

    Vậy $A = \frac{44}{75}$

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