[pentachoron]

If you gave credit to the source of the answers... then most teachers would just not give you the marks for the bits you copied. The cheating here is faking attribution - claiming yourself as a source of something you didn't originate, not copying - a legally and morally distinct thing to copyright infringement. Indeed, part of the point of copyright infringement is that you do know (and reveal to your clients) who made the thing you're copying, which is why it has value.