Riddle:
The teacher wrote on a blackboard: " x2 + 10x + 20 " Then all the pupils in the class came up in turn and either decreased or increased by 1 either the free coefficient or the coefficient at x, but not both. Finally they have obtained: " x2 + 20x + 10 ". Is it true that some time during the process there was written the square polynomial with the integer roots?
Python Solution:
Riddle source:
https://olympiads.win.tue.nl/imo/soviet/RusMath.html