Question

4, tìm x 

a, 4x.(x+1)=8.(x+1)                                  b , 3x.(x-2021)-x+2021=0

c, x.(x-1)-2.(1-x)=0

Answer 1

`4x.(x+1)=8.(x+1)`

`4x.(x+1)-8.(x+1)=0`

`4.(x+1).(x-2)=0`

`(x+1).(x-2)=0:4`

`(x+1).(x-2)=0`

`=>` \(\left[{}\begin{matrix}x+1=0\\x-2=0\end{matrix}\right.\)

`=>` \(\left[{}\begin{matrix}x=0-1=-1\\x=0+2=2\end{matrix}\right.\)

Vậy `x={-1;2}`

_______________________________

`3x.(x-2021)-x+2021=0`

`3x.(x-2021)-(x-2021)=0`

`(x-2021).(3x-1)=0`

`@TH1:`

`x-2021=0`

`x=0+2021`

`x=202`

`@TH2`

`3x-1=0`

`3x=0+1`

`3x=1`

`x=1:3`

`x=1/3`

Vậy `x = {2021;1/3}`

______________________

`x.(x-1)-2.(1-x)=0`

`(x-1).(x+2)=0`

`=>` \(\left[{}\begin{matrix}x-1=0\\x+2=0\end{matrix}\right.\)

`=>` \(\left[{}\begin{matrix}x=0+1=1\\x=0-2=-2\end{matrix}\right.\)

Vậy `x={-2;1}`