`|x-2018|+|2x-2019|+|3x-2020|=x-2021`
`=>|x-2018+2x-2019+3x-2020|=x-2021`
đkxđ `x-2021>=0`
`th1:x-2018+2x-2019+3x-2020>0`
`=>x-2018+2x-2019+3x-2020=x-2021`
`=>x-2018+2x-2019+3x-2020-x+2021=0`
`=>5x=4036`
`=>x=4036/5`
thay vào `VP=4036/5-2021<0`
`=>` vô nghiệm
`TH2:x-2018+2x-2019+3x-2020<0`
`=>x-2018+2x-2019+3x-2020=-x+2021`
`=>x-2018+2x-2019+3x-2020+x-2021=0`
`=>7x=8078`
`=>x=1154`
thay vào `VP:1154-2021<0`
`=>` pt vô nghiệm
vậy phương vô nghiệm