(−∞,3]∪[−3,∞)(-\infty, 3] \cup[-3, \infty)(−∞,3]∪[−3,∞)
(−∞,3](-\infty, 3](−∞,3]
[−3,3][-3,3][−3,3]
[3,∞)[3, \infty)[3,∞)
