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Homework Help: Time invariance. Proof help

  1. Oct 15, 2013 #1
    1. The problem statement, all variables and given/known data

    y(n)=x(4n+1). Is this system T.I or NOT T.I

    The professor marked this question wrong for my homework. He says it's NOT time invariant. I proved it is time invariant.

    2. Relevant equations

    System is time invariant if a shift in time in input results in the same shift in time when the output is shifted.

    3. The attempt at a solution
    shift in the x:
    y2=shift in y=y(n-n0)=x(4(n-n0)+1)

    They are the same, therefore they system is time invariant.
    The professor marked this problem wrong for me, and he gave me the run-around when I asked for him to prove it. Did I do this right?
  2. jcsd
  3. Oct 15, 2013 #2


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