Introduction to the challenge section

Coming ahead is the challenge section, in this section I'll put a set of challenges that will make you practice what you just learn. I'll want to give you some recommendations:

• Don't look at write ups or solutions, really try to do it by yourself.
• If you can't do it, then you are forgetting to do something, so recall your notes.
• Try to do your own write ups, include pictures and explanations.
• Google is your friend.