I am to use Cauchy's Multiplication Theorem and the Binomial Theorem in order to prove
$\exp(x+y)=\exp(x)\exp(y) $
but I have no idea where to begin. All I can think of doing is setting $\exp(x)$ as the sum to infinity of $(x^n)/n!$ and similarly for $\exp(y)$, $(y^n)/n!$