Seeing this I though this thing was promoted, and for avoiding for the question becoming boring, I didn't answer it suddenly and waited and I did mentioned that I knew the answer, maybe it's just misunderstanding that I don't know the answer. Anyways, what's the state/condition regarding such things?

See this and this. I edited one to include answer in question, I just didn't edited other just because.

• – quid Mar 7 '15 at 16:46
• Most of the time, you should not post a question on math.SE if you already know the answer. That is something that the StackExchange corporation encourages on other StackExchange sites, but it has never been a significant part of this site. And, in particular, this is not a site for "puzzles" or "challenges". The following post actually has no question at all: math.stackexchange.com/questions/1176622/… - because "I have solved this" is not a question. A question would be something that you want to know that you don't know. – Carl Mummert Mar 8 '15 at 3:03