Linearity
Linearity- A system is linear if a constant that multiplies an input to a system is also present in the output. Adding any number of linear combinations of complex numbers and functions of time together does not affect the linearity of the system.
A*x1(t) + B*x2(t) => A*y1(t) + B*y2(t) .... extendable for any amount of complex numbers (A, B, C...) and functions (x1, x2, x3...)
Linear System: Let x1[n] = 2n
x2[n] = 4n
