Instability results for certain systems of fourth and fifth order differential equations

摘要

The main purpose of this paper is to give sufficient conditions for the instability of the trivial solution for each of the following:X(4)+AX⃛+H(X,Ẋ,Ẍ,X⃛)Ẍ+G(X)Ẋ+F(X)=0,X(5)+AX(4)+BX⃛+H(Ẋ)Ẍ+G(X)Ẋ+F(X)=0,X(5)+Ψ(Ẍ)X⃛+Φ(Ẍ)+Θ(Ẋ)+F(X)=0.