How can we prove $(a_1+a_2+\cdots+a_n)^r\le a_1^r+ a_2^r+\cdots+a_n^r$ where each $a_i>0$ and $0<r<1$.
$(W_1+W_2+\cdots+W_n)^a \leq W_1^a +\cdots + W_n^a$ for $n$ integer, $n\geq 2$, $W\gt 0$ and $a$ constant, real, $0\lt a\lt 1$