A=200/14+200/35+200/65+……….+200/78209+200/79400

A=200/14+200/35+200/65+……….+200/78209+200/79400

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  1. `A=200/14+200/35+200/65+……….+200/78209+200/79400`

    `⇒A=400(1/28+1/70+1/130+……….+1/156418+1/158800`

    `⇒A=400(1/4.7+1/7.10+1/10.13+……….+1/394.397+1/397.400)`

    `⇒3A=400(3/4.7+3/7.10+3/10.13+……….+3/394.397+3/397.400)`

    `⇒3A=400(1/4-1/7+1/7-1/10+1/10-1/13+……….+1/394-1/397+1/397-1/400)`

    `⇒3A=400(1/4-1/400)`

    `⇒3A=400.99/400`

    `⇒3A=99`

    `⇒A=33`

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  2. Đáp án:

     

    Giải thích các bước giải:

    A=200/14+200/35+200/65+……….+200/78209+200/79400

    A= 400/28+ 400/70+ 400/130+….+ 400/156418 + 400/158800

    A= 400.( 1/28+ 1/70+….+ 1/158800)

    A= 400/3.( 3/4.7+ 3/7.10+…+ 3/397. 400)

    A= 400/3.( 1/4- 1/7+ 1/7- 1/10+…+ 1/397- 1/400)

    A= 400/3.( 1/4- 1/400)

    A= 400/3. 99/400

    A= 99/3

    A= 33

    Vậy A= 33

    Chúc bạn học tốt!

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