Đáp án:
`|x| = 20`
`⇒ x = 20` hoặc `x = -20`
Vậy `x ∈ {20 ; -20}`
`2 - |x| = 1`
`|x| = 2 - 1`
`|x| = 1`
`⇒ x = 1` hoặc `x = -1`
Vậy `x ∈ {1 ; -1}`
`|3 - x| - 2 = 5`
`|3 - x| = 5 + 2`
`|3 - x| = 7`
`⇒` \(\left[ \begin{array}{l}3-x = 7\\3-x = -7\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x = -4\\x = 10\end{array} \right.\)
Vậy `x ∈ {-4 ; 10}`
`|10 - x| = 3`
`⇒`\(\left[ \begin{array}{l}10 - x= 3\\10-x=-3\end{array} \right.\) ⇔ \(\left[ \begin{array}{l}x= 7\\x=13\end{array} \right.\)
Vậy `x ∈ {7 ; 13}`
