I'm having trouble with proving the binomial expansion with the principle of mathematical induction. I don't really know where to start, but I think that I managed to prove the first step. The inductive step is proving to be difficult:
Use the principle of mathematical induction to prove the binomial expansion: $$(x+y)^n=\sum_{i=0}^n {n \choose i}x^{n-i}y^i \quad{\forall} \quad n\in \Bbb Z^+$$
Thanks again!!