Let’s call Ω⊂Rn\Omega \subset \mathbb{R}^{n}Ω⊂Rn an open set. If 1≤p<∞1 \le p < \infty1≤p<∞ and u,v∈Lp(Ω)u, v \in L^{p}(\Omega)u,v∈Lp(Ω), then
∥u+v∥p≤∥u∥p+∥v∥p \left\| u + v \right\|_{p} \le \left\| u \right\|_{p}+\left\| v \right\|_{p} ∥u+v∥p≤∥u∥p+∥v∥p
This is called the Minkowski inequality.