Giúp mình với ạ. Chi tiết + dễ hiểu= ctrlhn+ 5* nha.

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Giúp mình với ạ. Chi tiết + dễ hiểu= ctrlhn+ 5* nha.
giup-minh-voi-a-chi-tiet-de-hieu-ctrlhn-5-nha

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Lệ Thu 5 years 2021-04-18T16:47:32+00:00 2 Answers 24 views 0

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    0
    2021-04-18T16:48:33+00:00

    Đáp án:

     

    Giải thích các bước giải:

     

    giup-minh-voi-a-chi-tiet-de-hieu-ctrlhn-5-nha

    0
    2021-04-18T16:49:15+00:00

    Đáp án:

    `x=21`

    Giải thích các bước giải:

    `(x-20).(1/2+1/3+1/4+…+1/200)/(1/199+2/198+3/197+…+198/2+199/1)=1/200`
    `=>(x-20).(1/2+1/3+1/4+…+1/200)/(1/199+2/198+3/197+…+198/2+199/1+(199-199))=1/200`
    `=>(x-20).(1/2+1/3+1/4+…+1/200)/(1/199+2/198+3/197+…+198/2+199/1+( \underbrace{1+1+1+…+1}_{\text{ Có 199 số 1}}-199))=1/200`
    `=>(x-20).(1/2+1/3+1/4+…+1/200)/((1/199+1)+(2/198+1)+(3/197+1)+…+(198/2+1)+(199/1+1)-199)=1/200`
    `=>(x-20).(1/2+1/3+1/4+…+1/200)/((1/199+199/199)+(2/198+198/198)+(3/197+197/197)+…+(198/2+2/2)+(199/1+1/1)-199)=1/200`
    `=>(x-20).(1/2+1/3+1/4+…+1/200)/(200/199+200/198+200/197+…+200/2+200 -199)=1/200`
    `=>(x-20).(1/2+1/3+1/4+…+1/200)/(200/199+200/198+200/197+…+200/2+200/200 )=1/200`
    `=>(x-20).(1/2+1/3+1/4+…+1/200)/(200.(1/199+1/198+1/197+…+1/2+1/200))=1/200`
    `=>(x-20). 1/200=1/200`
    `=>x-20=1/200:1/200`
    `=>x-20=1`
    `=>x=1+20`
    `=>x=21`
    Vậy `x=21`

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