I wouldn't want to do homework for other people, it deprives them of valuable learning. I've even seen a few people posting exam questions and even one question that appeared to be an in class quiz question of a snapshot of the board where the OP was asking for a quick solution (presumably before the quiz was done. These types of questions are offensive to me, because a student shouldn't be only concerned with the end result (the answer) but should be interested in the process of learning and how to come up with the correct answer.
If your going to post any question, make sure you take the time to format it and put some thought into it, instead of posting a question right out of the book\assignment.
However if you have a homework problem and prove that your working on it and your stuck I don't have a problem with answering that type of question provided that you've shown your attempt. SE is a site for students:
This site is for electronics and electrical engineering professionals, students, and enthusiasts. We ask and answer questions about electrical and electronics engineering topics, which include electronics, physical computing, and those working with microcontrollers, Arduinos and embedded systems.