Let A= (aij)∈C^n×n and r,. =∑j≠i |aij|. Suppose that for each row of A there is at least one nonzero off-diagonal entry. It is proved that all eigenvalu
Let G be a graph,for any u∈V(G),let N(u) denote the neighborhood of u and d(u)=|N(u)| be the degree of u. For any U V(G) ,let N(U)=Uu,∈UN(u), and d(U)=|N(U)|.
Yang et al gave some criteria of prequasi-invex functions,semistrictly prequasi-invex functions and strictly prequasi-invex functions in 2001,under a certain se