MathDB

factions from State Duma - All-Russian MO 1997 Regional (R4) 11.5

Source:

September 24, 2024

combinatorics

Problem Statement

Members of the State Duma formed factions in such a way that for any two fractions

A

and

B

(not necessarily different),

\overline{A \cup B}

is also faction (

\overline{C}

denotes the set of all members of the Duma, not including in

C

). Prove that for any two factions

A

and

B

A \cup B

is also a faction.