Giải thích các bước giải:
| x | ≥ 2
⇔ \(\left[ \begin{array}{l}x ≥ 2\\x ≤ -2\end{array} \right.\)
| x | ≤ 2
⇔\(\left[ \begin{array}{l}x ≤ 2\\x ≥ -2\end{array} \right.\)
`x^2` ≥ 2
⇔ \(\left[ \begin{array}{l}x ≥ \sqrt{2} \\x ≤ \sqrt{-2} \end{array} \right.\)
`x^2` ≤ 2
⇔ \(\left[ \begin{array}{l}x ≤ \sqrt{2}\\x ≥ \sqrt{-2}\end{array} \right.\)