## Oscillation criteria for second order differential equations with positive and negative coefficients.(English)Zbl 1110.34046

Summary: Some oscillation criteria for the second-order neutral delay differential equations $\left[x(t)\pm\sum^l_{i=1}c_i(t)x(t-\tau_i) \right]''+\sum^m_{i=1} p_i(t)x(t-\delta_i)-\sum^n_{i=1}q_i(t)x(t-\sigma_i)=0,\;t>0,$ are established. New oscillation criteria are different from one recently established in the sense that the boundedness of the solution in the results of N. Parhi and S. Chand [J. Indian Math. Soc., New Ser. 66, 227–235 (1999; Zbl 1141.34340)] has been erased., i.e., we give sufficient conditions for the oscillation of all solutions.

### MSC:

 34K11 Oscillation theory of functional-differential equations 34K40 Neutral functional-differential equations

Zbl 1141.34340
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### References:

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