Đáp án:
`x=2020`
Giải thích các bước giải:
`x/2020+(x+1)/2021+(1-x)/2019+(2-x)/2018=0`
`\to (x/2020-1)+((x+1)/2021-1)+((1-x)/2019+1)+((2-x)/2018+1)=0`
`\to (x-2020)/2020+(x+1-2021)/2021+(1-x+2019)/2019+(2-x+2018)/2018=0`
`\to (x-2020)/2020+(x-2020)/2021+(2020-x)/2019+(2020-x)/2018=0`
`\to (x-2020)/2020+(x-2020)/2021-(x-2020)/2019-(x-2020)/2018=0`
`\to (x-2020)(1/2020+1/2021-1/2019-1/2018)=0`
Vì `1/2020>(-1)/2019`
`1/2021>(-1)/2018`
`\to 1/2020+1/2021>(-1)/2019-1/2018`
`\to 1/2020+1/2021-1/2019-1/2018>0`
`\to x-2020=0`
`\to x=2020`
Vậy `x=2020`
