Maxima of the $Q$-index of non-bipartite $C_3$-free graphs

Ruifang Liu, Lu Miao, Jie Xue

A classic result in extremal graph theory, known as Mantel's theorem, states that every non-bipartite graph of order $n$ with size $m>\lfloor \frac{n^2}{4}\rfloor$ contains a tri…