题目

Dear Editor. I’m a middle school student named Li Hua. I’m writing tell you something. Recently I noticed that many of my schoolmates often go to the Internet bar near our school. The other day, I went there, either. I was surprising to see many students playing computer games, seeing movies or were chatting. Some students were even sending love letter online. In my opinion, Internet bar should be a place which we can find much usefully information. Internet should be a window to the outside world rather than a place for playing games. Internet is good unless we make good use of it由x,-x,｜x｜,x2,-3x3组成的集合中,元素的个数最多为几个？