Homology Theorem

This lecture covers the proof of Theorem A, focusing on an example related to simplicial and singular homology, the Mayer-Vietoris sequence, naturality, and excision. The theorem states that for a good pair (X,A), the quotient map induces isomorphisms between homology groups. It also discusses the concept of deformation retracts and open neighborhoods. The lecture emphasizes the importance of understanding homotopy equivalences and the commutative diagrams involved in the proof.