MathDB

Ari and Beri play a game using a deck of

2020

cards with exactly one card with each number from

1

2020

. Ari gets a card with a number

a

and removes it from the deck. Beri sees the card, chooses another card from the deck with a number

b

and removes it from the deck. Then Beri writes on the board exactly one of the trinomials

x^2-ax+b

x^2-bx+a

from his choice. This process continues until no cards are left on the deck. If at the end of the game every trinomial written on the board has integer solutions, Beri wins. Otherwise, Ari wins. Prove that Beri can always win, no matter how Ari plays.

Problem Statement