The graphic that follows represents a discrete time function.

Make ρ = 8.To the left of ρ, the samples are zero. After ρ (inclusive), they are equal to the unit.

Create this function using only sums and subtractions, and multiplications by constants:

T_initial =       T_end =

u_-1(k) =

Create the function again, this time you can also use multiplication of functions:

T_initial =       T_end =

u_-1(k) =