Provided $\displaystyle \[{x_i} > 0\]$ where $\displaystyle \[i = \overline {1,n} \]$

I am asked to prove

$\displaystyle \displaystyle\[\sqrt[n]{\prod\limits_{i = 1}^n {{x_i}} } \le \frac{{\sum\limits_{i = 1}^n {{x_i}} }}{n}\]$

Since this seems to be a pretty specific problem - either you know the concept or you don't - I do not have any of my own thoughts to share...