Câu 2. (2 điểm) Tìm x biết: a) $\frac{1}{4}$ + x = $\frac{1}{2}$ b) ($\frac{1}{3}$ - $\frac{1}{6}$x)(x + $\frac{1}{2}$) = 0 c) |x + $\frac{1}{3}$| + $\frac{1}{6}$ = $\frac{11}{2}$

Đáp án+Giải thích các bước giải:

 `a)`

`1/4+x=1/2`

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

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

`=>x=1/4`

Vậy `x=1/4`

`b)`

`(1/3-1/6x).(x+1/2)=0`

`+)TH1:1/3-1/6x=0`

`=>-1/6x=-1/3`

`=>x=1/3: 1/6`

`=>x=1/3. 6`

`=>x=2`

`+)TH2:x+1/2=0`

`=>x=0-1/2`

`=>x=-1/2`

Vậy `x\in{2;-1/2}`

`c)`

`|x+1/3|+1/6=11/2`

`=>|x+1/3|=11/2-1/6`

`=>|x+1/3|=33/6-1/6`

`=>|x+1/3|=32/6`

`=>|x+1/3|=16/3`

`+)TH1:x+1/3=16/3`

`=>x=16/3-1/3`

`=>x=15/3`

`=>x=5`

`+)TH2:x+1/3=-16/3`

`=>x=-16/3-1/3`

`=>x=-17/3`

Vậy `x\in{5;-17/3}`