... (1.1)isoscillatorybyCorollary 2.8.RemarkthatCorol-lary 2.9 cannot be used in this case.OSCILLATORY MIXED DIFFERENCE SYSTEMSJOS´E M. FERREIRA AND SANDRA PINELASReceived 2 November 2005; Accepted ... can conclude, by Theorem 2.3, that the correspondent system (1.1) is oscillatory.12 Oscillatory mixed difference systemsTherefore, for every λ>1, we have by (3.1)i=1λ−iαPi≤0,mj=1λjβQj≤0, ... sumi=2b(Pi) =0, then we obtain by (3.3)μM(λ)≤i=1bPi≤−1 <λ−1 (3.13)2 Oscillatory mixed difference systemsinitial values x−, ,x0, ,xm−1, denoting by I the d ×d identity matrix,...