Bài 2 (2 điểm) Tìm x, biết: a) $\frac{2}{5}$ - x = 1$\frac{1}{5}$ b) $\frac{2}{3}$ : x + $\frac{1}{3}$ = 4 c) (x - $\frac{1}{2}$).(x + $\frac{3}{7}$) = 0

Đáp án+Giải thích các bước giải:

`a)`

`2/5-x=1 1/5`

`=>x=2/5- 1 1/5`

`=>x=2/5-(1+1/5)`

`=>x=2/5-1-1/5`

`=>x=1/5-1`

`=>x=1/5-5/5`

`=>x=-4/5`

Vậy `x=-4/5`

`b)`

`2/3:x+1/3=4`

`=>2/3:x=4-1/3`

`=>2/3:x=12/3-1/3`

`=>2/3:x=11/3`

`=>x=2/3: 11/3`

`=>x=2/3. 3/11`

`=>x=2/11`

Vậy `x=2/11`

`c)`

`(x-1/2).(x+3/7)=0`

`+)TH1:x-1/2=0`

`=>x=1/2`

`+)TH2:x+3/7=0`

`=>x=-3/7`

Vậy `x\in{1/2;-3/7}`