(2,∞](2, \infty](2,∞]
(−∞,−2]∪[2,∞)(-\infty,-2] \cup[2, \infty)(−∞,−2]∪[2,∞)
{2,−2}\{2,-2\}{2,−2}
[−2,2][-2,2][−2,2]