Hi nunos
I suggest using mathematical induction
I already know about that, but thanks for the suggestion anyway. I am going to write here, what I have so far, and hopefully you or someone will point me in the right direction.
Proving for n = 1, easy.
Assuming it's true for n, let's evaluate for n+1.
And I don't know how to go from here... I don't even know if what I've done is relevant...