Graph Theory, Lecture 17: Extremal graph theory II: Dense graphs

Notion of extremal; difference to maximal. Motivation and definition of Turán graphs. Turán's Theorem 7.1.1 with structural proof (from 8:00) [induction hypothesis used at 22:58, 26:20, 27:47] and Zykov's proof (by vertex duplication, from 32:00). Erdös-Stone Theorem 7.1.2 and discussion of statement. Deduction of Erdös-Simonovits application: ex(n,H) for arbitrary H (from 51:00). Covers Chapter 7.1. Based on R.Diestel, Graph Theory, Springer GTM173, 6th edition 2025. Ebooks available at https://diestel-graph-theory.com under links "Standard eBook" and "Professional Edition".