tìm x biết x-1/2019 +x-2/2018+x-3/2017=3

Đáp án:

`(x-1)/2019+(x-2)/2018+(x-3)/2017=3`

`<=>(x-1)/2019+(x-2)/2018+(x-3)/2017-3=0`

`<=> ((x-1)/2019 -1)+((x-2)/2018 -1)+((x-3)/2017 -1)=0`

`<=> (x-2020)/2019+(x-2020)/2018+(x-2020)/2017=0`

`<=> (x-2020).(1/2019+1/2018+1/2017)=0`

Mà `1/2019+1/2018+1/2017>0`

`<=> x-2020=0`

`<=> x=2020`