The official posted policy states: Feel free to ask for help on your subject, but simply posting your homework question verbatim and expecting an answer is rude! We’re not here to do your homework for you.
Now, as someone who likes to answer math questions, this sometimes poses a dilemma. Oftentimes the questioner is genuinely stumped on how to proceed to tackle a problem, and while it’s easy to just say, “Do your own homework and leave us alone, you lazy, clueless parasite!”, I think it’s perfectly justifiable and appropriate for me (the answerer) to completely work through certain problems, showing all steps for at least one of them, with the expectation that the questioner will thereby learn by example and be able to answer similar problems comprising the rest of their assignment.
Some Q&A sites are overly supportive of doing others’ homework in this manner (AnswerBag comes to mind—where kids routinely dump whole boatloads of homework assignments so they can go off & play video games while others toil at their work). Fluther, on the other hand, is IMHO a little too unreceptive—even hostile—to homework support.
I try to at least work a problem partway through, sometimes stopping short of the final answer. As they say in math textbooks, “the details are left to the reader as an exercise.” Other times I think a complete solution is necessary in order to help the questioner. As always, a good question makes its intentions clear and a good answer relies on judging what’s appropriate for the question.