One important problem in system analysis is to determine, see Figure 1, the output (or
response) y(t) or y[k] of a system stimulated by a known input signal u(t) or u[k], where x(t)
or x[k] denotes continuous-time or discrete-time signals and systems, respectively. If the
system is memoryless, the relationship between the input and output can generally be
described by an algebraic function where the solution can be determined directly though
algebraic manipulations: addition, subtraction, multiplication, and division.