- #1
TaPaKaH
- 54
- 0
Suppose we have a function ##f:\mathbb{N}\times\mathbb{N}\to\mathbb{R}_+## that is
- increasing: ##f(x+e_i)\geq f(x)## for any ##x\in\mathbb{N}^2## and ##i\in\{1,2\}##;
- convex: ##f(x+2e_i)-f(x+e_i)\geq f(x+e_i)-f(x)## for any ##x\in\mathbb{N}^2## and ##i\in\{1,2\}##.