The question you asked has properties very similar to several questions asked by others, so it really is just the pattern that set off a "possible homework" alarm. We are more than willing to help. If we know it is homework, we tend to take a more hands off approach (or at least try to) and try to guide instead just answering the question.

We want people to understand what they are doing. For real world questions, we'll answer than normal work backward on the understanding side because you are still the one who will get the call at 3:30 in the morning when things break, not us.