ABSTRACT
When one studies systems, one studies the interactions and behavior of an assemblage of things when subjected to certain conditions. In its simplest case, a system can have one input and one output. If one can determine the input by measuring the output, then the system under consideration is said to be invertible. If two inputs give the same output then the system is not invertible. This chapter indicates that any signal can be represented as a sum of weighted impulse. It discusses differential equations and physical systems, homogeneous differential equations and their solutions, and nonhomogeneous differential equations and their solutions. If the coefficients of the characteristic equation have the same sign, then the system is stable. If there are sign changes in the coefficients of the characteristic equation, one can test stability by finding the roots of the characteristic equation analytically, or one can use the MATLAB function “roots” to find the roots of the characteristic equation.
