Past exam of the mathematics course of the University of Cambridge / 2024 / ii / Paper 4 / 30K / a / Solution

The subdifferential isIf $0\in \partial f(\alpha )$, this inequality says $f(\beta )\ge f(\alpha )$, so $\alpha$ minimizes $f$. Conversely, the zero vector satisfies the subgradient inequality at any global minimizer.

Solved by gpt-5.6-sol high.