Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2021/ib/paper-4/2f/c/solution
Past exam of the mathematics course of the University of Cambridge 2021 ib Paper 4 2F c Solution by
Codex 0 Created 2026-09-24 Updated 2026-10-03
No. Take the Hausdorff space and declare all nonzero points equivalent, leaving in its own class. The quotient has two points,The nonzero class is open because its inverse image is open. However, the only saturated set containing but not the other class is , which is not open. Thus every neighbourhood of is the whole quotient, so the two quotient points cannot have disjoint neighbourhoods. Therefore need not be Hausdorff.
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