-Tìm x;y;z E Q biết: a)|x+13/7|+|y+2020/2019|+|z-2018|=0 b)|x-1/2|+|y+3/2|+|z-5/2|<0

Question

-Tìm x;y;z E Q biết:
a)|x+13/7|+|y+2020/2019|+|z-2018|=0
b)|x-1/2|+|y+3/2|+|z-5/2|<0

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Isabelle 5 tháng 2021-07-23T08:49:51+00:00 1 Answers 17 views 0

Answers ( )

    0
    2021-07-23T08:51:21+00:00

    a, Do

    `|x+13/7| ≥ 0 ; |y+2020/2019|≥0;|z-2018|≥0`

    `=>|x+13/7|+|y+2020/2019|+|z-2018|≥0`

    Do đó để `|x+13/7|+|y+2020/2019|+|z-2018|=0` thì

    `x+13/7=y+2020/2019=z-2018=0`

    `=> x = -13/7 ; y = -2020/1019 ; z = 2018`

    b, Do

    `|x-1/2|≥0;|y+3/2|≥0;|z-5/2|≥ 0`

    `=> |x-1/2|+|y+3/2|+|z-5/2|≥0`

    `=>|x-1/2|+|y+3/2|+|z-5/2|<0` (vô lí)


    `=> x ; y ; z ∈ ∅`

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