Adivar, MuratRaffoul, Youssef N.2023-06-162023-06-1620110895-7177https://doi.org/10.1016/j.mcm.2011.03.027https://hdl.handle.net/20.500.14365/1333We use Lyapunov functionals to obtain sufficient conditions that guarantee exponential decay of solutions to zero of the time varying delay differential equation x'(t) = b(t) x(t) - a(t) x(t - h(t)). The highlights of the paper are allowing b( t) to change signs and the delay to vary with time. In addition, we obtain a criterion for the instability of the zero solution. Moreover, by comparison to existing literature we show effectiveness of our results. (C) 2011 Elsevier Ltd. All rights reserved.eninfo:eu-repo/semantics/openAccessExponential stabilityInstabilityLyapunov functionalTime delayArticle10.1016/j.mcm.2011.03.0272-s2.0-79955477021