2. Unconstrained Optimization

#2.1 Basic Results on the Existence of Optimizers ## 2.1. Let $f:U->\mathbb{R}$ be a function on a set $U\subseteq \mathbb{R}^n$. Let $x^*\in U$ be an arbitrary point, and let $B_r(x^*):=\{x\in U:|| x-x^*||