Câu 1: `|-2x+1|` $=$ `7`
`\text{TH1:}` `-2x+1` $=$ `7` `\text{TH2:}` `-2x+1` $=$ `-7`
`⇔``-2x` $=$ `7`$-$`1` `⇔``-2x` $=$ `(-7)`$-$`1`
`⇔``-2x` $=$ `6` `⇔``-2x` $=$ `-8`
`⇔``x` $=$ `6``:``(-2)` `⇔``x` $=$ `(-8)``:``(-2)`
`⇔``x` $=$ `-3` `⇔``x` $=$ `4`
Câu 2: `3.|x-4|` $=$ `(-14)+29`
`⇔``3.|x-4|` $=$ `15`
`⇔``|x-4|` $=$ `15:3` $=$ `5`
`\text{TH1:}` `x-4` $=$ `5` `\text{TH2:}` `x-4` $=$ `-5`
`⇔``x` $=$ `5`$+$`4` `⇔``x` $=$ `(-5)`$+$`4`
`⇔``x` $=$ `9` `⇔``x` $=$ `-1`
