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Lemma 1.3.3: Sequences and Their Limits

Understanding how sequence properties relate to limits

Part 1: Sequence Terms Stay Within r of the Limit

For any rational r > 0, we have x − r ≤ xₙ ≤ x + r eventually.

11.52xx+rx−rN=3k (sequence index)Before NAfter N (in band)[x−r, x+r]

Key observation

No matter how small you make r, there is always some N after which all sequence terms xₙ fall within the band [x−r, x+r]. This is exactly the visual meaning of "xₙ → x".