Given the following inequality:
$$\sqrt[N]{\prod_i^N x_i} < \frac{1}{N} \sum_i^N x_i$$
for $x_i \in \mathbb{R^+_0}$ (positive reals) and $N \in \mathbb{N}^+$ (positive integer).
How can I prove that it is valid for the above conditions?
BTW: what is the english word for the $\prod$ operation? It has a name in spanish (multiplicatoria or productoria) but I have not been able to find a name for it in english other than "product".