2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/123066Let $R$ be a commutative ring with identity. Let $Γ(R)$ be a graph with vertices as elements of $R$, where two distinct vertices $a$ and $b$ are adjacent if and only if $Ra+Rb=R$. In this paper we consider a subgraph $Γ_2(R)$ of $Γ(R)$ which consists of non-unit elements. We look at the connectedness and the diameter of this graph. We completely characterize the diameter of the graph $Γ_2(R)\setminus\J(R)$. In addition, it is shown that for two finite semi-local rings $R$ and $S$, if $R$ is reduced, then $Γ(R)\congΓ(S)$ if and only if $R\cong S$.8 PagesCommutative AlgebraCombinatorics05C75; 13A15text