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ON A FUNCTIONAL EQUATION FOR QUADRATIC INVARIANT CURVES
Zhang, Weinian Korean Mathematical Society 2001 대한수학회지 Vol.38 No.6
Quadratic invariant curve is one of the simplest nonlinear invariant curves and was considered by C. T. Ng and the author in order to study the one-dimensional nonlinear dynamics displayed by a second order delay differential equation with piecewise constant argument. In this paper a functional equation derived from the problem of invariant curves is discussed. Using a different method from what C. T. Ng and the author once used, we define solutions piecewisely and give results in the remaining difficult case left in C. T. Ng and the authors work. A problem of analytic extension given in their work is also answered negatively.
DISTRIBUTION OF ROOTS OF CUBIC EQUATIONS
Deqing Huang,Yilei Tang,Weinian Zhang 한국수학교육학회 2010 純粹 및 應用數學 Vol.17 No.2
In this note the distribution of roots of cubic equations in contrast to 0is given, which is useful to discuss eigenvalues for qualitative properties of differential equations.