Question 5
Find all natural numbers $n\gt 1$ for which
$$\sum_{k=1}^n x_k^2\ge x_n\sum_{k=1}^{n-1}x_k$$
holds for every choice of $x_k$, $k=1,\ldots,n$.
$$\sum_{k=1}^n x_k^2\ge x_n\sum_{k=1}^{n-1}x_k$$
holds for every choice of $x_k$, $k=1,\ldots,n$.