2 problems

Let $q$ be a power of an odd prime, and let $ER_q$ be the polarity graph associated with the orthogonal polarity of $PG(2,q)$. An absolute point is a vertex corresponding to a poin…

Let $C_4$ denote the cycle on four vertices, and let $\mathrm{Ex}(n,C_4)$ be the family of extremal $C_4$-free graphs on $n$ vertices. An induced subgraph is obtained by selecting…