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GATE 2023 MA – Question 53

Real Analysis · Metric Spaces and Continuity · 2 marks · Multiple select

In C[0,1] with supremum metric, let f_n(x)=xⁿ and P={f_n:n∈ℕ}. Which hold?

  1. P is totally bounded.
  2. P is bounded.
  3. P is closed.
  4. P is open.

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Show answer and explanation

Correct answer: (B) P is bounded.; (C) P is closed.

Explanation

All norms equal 1, proving boundedness. If a sequence of distinct exponents tends to infinity, its pointwise limit is zero on [0,1) and one at 1, hence it cannot converge uniformly to a continuous function. Any convergent sequence from P must therefore have bounded exponents and its limit belongs to P: P is closed. The subsequence x^(2^k) is pairwise separated by at least 1/4 (maximize t−t²), refuting total boundedness. Small constant perturbations leave P, refuting openness. **B,C**.

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