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## Homework Statement

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.

## Homework Equations

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

## The Attempt at a Solution

shift in the x:

y1=x(4(n-n0)+1)

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?