I can bring you joy or sorrow, or everything in between. None have seen, smelt or felt me, yet many still know what I am. I have many types, but I am really just one thing. What am I?
Bạn thử chứng minh "3n = 4 với mọi n" thử xem nào?
3n = Ba n
4 = Bốn = Bố n