Consider a real-valued sequence x[n] for which One value of x[n] may have been...

Consider a real-valued sequence x[n] for which

One value of x[n] may have been corrupted, and we would like to approximately or exactly recover it. With denoting the corrupted signal,

and

(a) The value of n₀ is known.

(b) The exact value of n₀ is not known, but we know that n₀ is an even number.

(c) Nothing about n₀ is known.