1.2.3+2.3.4+3.4.5+…..+2018.2019.2020

Question

1.2.3+2.3.4+3.4.5+…..+2018.2019.2020

in progress 0
Cherry 5 years 2021-05-24T00:10:12+00:00 2 Answers 30 views 0

Answers ( )

  1. Helga
    0
    2021-05-24T00:11:42+00:00
    Reply

    Đáp án:

    $\rm 2018.2019.505.2021$ 

    Giải thích các bước giải:

    Đặt $\rm S= 1.2.3+2.3.4+3.4.5+…..+2018.2019.2020$

    $\rm 4S=1.2.3.4+2.3.4.4+….+2018.2019.2020.4$

    $\rm 4S=1.2.3.4+2.3.4.(5-1)+….+2018.2019.2020.(2021-2017)$
    $\rm 4S=1.2.3.4+2.3.4.5-1.2.3.4+…+2018.2019.2020.2021-2017.2018.2019.2020$

    $\rm 4S=2018.2019.2020.2021$

    $\rm S=\dfrac{2018.2019.2020.2021}{4}=2018.2019.505.2021$

  2. thienthi
    0
    2021-05-24T00:11:59+00:00
    Reply

    $\text{Đáp án + Giải thích các bước giải:}$

    `T=1.2.3+2.3.4+3.4.5+….+2018.2019.2020`

    `=>4T=1.2.3.4+2.3.4.4+3.4.5.4+….+2018.2019.2020.4`

    `=>4T=1.2.3.4+2.3.4.(5-1)+3.4.5.(6-2)+…+2018.2019.2020.(2021-2017)`

    `=>4T=1.2.3.4+2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+….+2018.2019.2020.2021-2017.2018.2019.2020`

    `=>4T=2018.2019.2020.2021`

    `=>T=2018.2019.505.2021`

     

Leave an answer

Browse

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