Part E. Linearity and Time Invariance
A discrete-time system is such that when the input is one of the signals in the left column, then the output is the corresponding signal in the right column:
| Input | Output | |
| X0[n]=δ[n] | Y0[n]=δ[n-1] | |
| X1[n]=δ[n-1] | Y1[n]=4δ[n-2] | |
| X2[n]=δ[n-2] | Y2[n]=9 δ[n-3] | |
| X3[n]=δ[n-3] | Y3[n]=16 δ[n-4] | |
| ... | ... | |
| Xk[n]=δ[n-k] | Yk[n]=(k+1)^{}2 δ[n-(k+1)] |
For any non-negative integer k
