Finally!

A very very big thanks to you guys for your help.
It is my first time proving something in math, so it was a very good problem to tackle as it is going to get harder from here...
The teacher don't help too much so it was very fortunate for me to have you explain how to do this right.
Now whats left is for my teacher to check it (and the other problems I solved) and rate it, we'll see how much I get...

Thanks a lot again!