Sources for problem
https://old.reddit.com/r/math/comments/cy7u04/a_very_simple_but_tricky_question_from_finnish/
@rizka commented with a link to the 2014 exam (in Finnish). It is question 4:
https://yle.fi/progressive/fynd/oppiminen/oppiminen.yle.fi/yo-kokeet/matematiikka_pitka.pdf
Quadratic equation history (Brahmagupta)
https://www-history.mcs.st-and.ac.uk/HistTopics/Quadratic_etc_equations.html
https://en.wikipedia.org/wiki/Quadratic_equation#History
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