System: $ X_{k}[n-k] \to Y_{k}[n] = (k+1)^2 \delta [n-(k+1)] $
$ X_{k}[n] \to timedelay \to sys \to Z_{k}[n]= $
$ X_{k}[n] \to sys \to timedelay \to Z_{k}[n]= $
Since is equal to , the system is time-invariant.
