The. Multi Delay Ndde Stability Is Necessary And Sufficient Condition And The Solution Of Linear Ndde

Consider the first-order NDDE x?t) + cx (t ?r) + azd~t) + bx(t ?= 0 and chawcteristic equation~ ,t+k~ 鱝+b&2d =0 (1) (2) Where a. b. c. rare constaats, r >0. In this paper, we give the analytic formul~ of Eq. (1) and establish necessary and sufficient conditions for the roots of Eq. (2) having negative real parts, which will be helpful in predictb~g stability or instability directly from the coefficients of the given equation, and is easy to verify and apply. These results are complete, and contain the corresponding results in [l]-[5].