giúp mình nha gggg

Question

giúp mình nha gggg
giup-minh-nha-gggg

in progress 0
Tryphena 5 years 2021-05-20T17:24:41+00:00 2 Answers 31 views 0

Answers ( )

  1. Bo
    0
    2021-05-20T17:25:53+00:00
    Reply

    Đặt `B= 29/1 + 28/2 +27/3+…+2/28 + 1/29`

    `B= (28/2+1) + (27/3+1)+…+(1/29 +1) + (29/1+1)`

    `B= 30/2 + 30/3 +…+30/29 + 30/30`

    `B= 30(1/2 +1/3+…+1/29+1/30)`

    => `A = (30(1/2+1/3+…+1/29+1/30))/(1/2+1/3+1/4+…+1/30)`

    => `A= 30`

    Vậy `A=30`

     

  2. King
    0
    2021-05-20T17:26:22+00:00
    Reply

    Giải thích các bước giải:

    $ A=\dfrac{ \dfrac{29}{1} + \dfrac{28}{2} + \dfrac{27}{3} + … + \dfrac{3}{27} + \dfrac{2}{28} + \dfrac{1}{29}} { \dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+…+\dfrac{1}{29}+\dfrac{1}{30}}$

    $\\$
    Đặt `B = 29/1 + 28/2 + 27/3 + … + 3/27 + 2/28 + 1/29`
    `=> B = (28/2 + 1 ) + (27/3+ 1 )  + … + (3/27+ 1 )  + (2/28+ 1 )  + (1/29+ 1 ) + 1 `
    `=> B = 30/2 + 30/3 + … + 30/27 + 30/28 + 30/29 + 30/30`
    `=> B = 30. ( 1/2 + 1/3 + … + 1/27 + 1/28 + 1/29 + 1/30)`
    $\\$
    Vậy `A`=$\dfrac{ 30.(\dfrac{1}{2}+\dfrac{1}{3}+…+\dfrac{1}{28}+\dfrac{1}{29}+\dfrac{1}{30})} { \dfrac{1}{2}+\dfrac{1}{3}+….+\dfrac{1}{29}+\dfrac{1}{30}}$ `= 30`

Leave an answer

Browse

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