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Erdős problem 209

Let AA be a finite collection of d≥4d\geq 4 non-parallel lines in R2\mathbb{R}^2 such that there are no points where at least four lines from AA meet. Must there exist a 'Gallai triangle' (or 'ordinary triangle'): three lines from AA which intersect in three points, and each of these intersection points only intersects two lines from AA?

Erdős Problems records this as disproved (Lean).

No Repository has ruled on it here.

How far the record reaches4 of 6 stages
  1. Sourceerdos-problems
  2. StatementRetained
  3. Formal1 retained
  4. Resolutiondisproved (Lean)
  5. WorkNone recorded
  6. DecisionNone here
  7. The questionNot reached
What this record is missingWork

Nothing here has checked that finding.

Reproducing it here turns a report into evidence.

Where the source files it109 share a topic
Erdős problem 94accepted
Carrying a Standing. Browse the topic.