-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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1. 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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