[−1,1][-1,1][−1,1]
(−∞,−1]∪[1,∞)(-\infty,-1] \cup[1, \infty)(−∞,−1]∪[1,∞)
(−∞,0]∪[2,∞)(-\infty, 0] \cup[2, \infty)(−∞,0]∪[2,∞)
[0,2][0,2][0,2]
