About sections 20, 22, 23 and self-study

Section 20: concentrate on statements of Thm 20.10, Cor 20.11, Thm 20.12, Cor 20.13. Read carefully Examples 20.14 and 20.15

Section 22: Polynomials should be familiar. Concentrate on Thm 22.4 and its proof, Examples 22.6-9 and the small section "The new approach".

Section 23: concentrate on statements of Thm 23.1, Cor. 23.3 and its proof, Cor 23.5 and its proof, statement of Cor. 23.6, Thm 23.10 and its proof, statement of Thm 23.11, Cor 23.12 and its proof. Read Examples 23.2-14.