Q:

Is it not allowed to answer ones own question?

I recently posted this question, Length of median extended to the circumcircle . Since there is an option to give an answer of, along with question, saying - share your knowledge, Q&A-style, and a link saying that it is explicitly encouraged. However, when I posted the question, along with the answer, and I suppose there was nothing wrong with the question and answer itself, I was immediately downvoted and a close vote was put upon.   
So, why this behaviour? Isnt it explicitly encouraged now? 

A:

It is allowed. But self-answered questions receive additional amount of scrutiny; in some users' opinion (including mine) they need more to justify their existence than "regular" questions. 
If it's a result to which you or other users are likely to refer later, self-answered question makes perfect sense. But yours looks like a puzzle in which you gave away the secret immediately. What use is it now? 
It's also possible that voters did not scroll down to see that you were the one who answered. They read the question, thought "homework dump", and reacted. 
Related: 

Large number of self-answered questions permissible?
Answering your own question 
Is answering own question okay?

