In this paper through a further discussion about the two macroeconomic models in document[1],we get a good theorem about solutions of the models,and point out that the policies which the government seeks lie on the design of the social welfare function,and at the same time it has close relations with the constants system which the models have given.

Differential operator method for particular solution for second-order constant coefficient linear differential equation;

A formula to the solutions of initial value problems of linear differential equations with constant coefficients;

A formula to solve initial value problem of nonhomogeneous linear differential equations with constant coefficients;

Toeplitz matrix for inhomogeneous linear difference equation with constant coefficients

This paper is devoted to providing a particular solution to find a kind of systems of three-dimensional second order differential equations with constant coefficients by means of undetermined coefficients.

general term formula is a important path to research and study number sequence problem,a tentative study of constant coefficients homogeneous linear recurrent number sequence general term formula,give two theorem to dispose of general ter m formula.

New stability criterion for linear system with constant complex coefficients;