Tunc, CemilTunc, Ercan2025-05-102025-05-1020061072-66912-s2.0-33748708836https://hdl.handle.net/20.500.14720/17476Our goal in this paper is to obtain sufficient conditions for instability of the zero solution to the non-linear vector differential equation X + F(X, (X) over dot))X + G((X) over dot) + H(X) = 0. An example illustrates the results obtained.eninfo:eu-repo/semantics/closedAccessInstabilityLyapunov'S Second (Or Direct) MethodNonlinear Differential Equations Of Third OrderArticle