The GATE Grind

GATE 2026 MA – Question 47

Topology · Countability and Separation · 2 marks · Multiple choice

A map f:X→Y is continuous and bijective. Which condition guarantees it is a homeomorphism?

  1. X and Y are compact.
  2. X is Hausdorff and Y compact.
  3. X is compact and Y Hausdorff.
  4. X and Y are Hausdorff.

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Correct answer: (C) X is compact and Y Hausdorff.

Explanation

If X is compact, every closed subset of X is compact. Its image under continuous f is compact and therefore closed in Hausdorff Y. Thus f is a closed bijection and f⁻¹ is continuous. This proves **C**; the other conditions alone do not ensure a continuous inverse.

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