(−∞,−1)∪(1,−∞)(-\infty,-1) \cup(1,-\infty)(−∞,−1)∪(1,−∞)
[−1,1][-1,1][−1,1]
(−∞,∞)(-\infty, \infty)(−∞,∞)
(−∞,−1]∪[1,∞)(-\infty,-1] \cup[1, \infty)(−∞,−1]∪[1,∞)