`a) | 3x | = 0`
`⇔ 3x = 0`
`⇔ x = 0 : 3`
`⇔ x = 0`
Vậy `, x = 0 .`
`b) | x - 1/3 | = 2 1/5`
`⇔ | x - 1/3 | = 11/5`
`⇔` \(\left[ \begin{array}{l}x - \frac{1}{3} = \frac{11}{5}\\x - \frac{1}{3} = \frac{- 11}{5}\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x = \frac{38}{15}\\x = \frac{- 28}{15}\end{array} \right.\)
Vậy `, x ∈ { 38/15 ; ( - 28 )/15 } .`
`c) | x + 2 | = - 5 (` Vô lý `)`
`⇒ x` không tồn tại `⇒ x ∈ ∅`
Vậy `, x ∈ ∅ .`
