Quadratics
(Published on 23. February 2026, 03:41 by Prof.Dori)
Quadratics
Rules:
Normal sudoku rules apply.
Quads: Each circle contains four invisible digits (not necessarily distinct and to be deduced). These must each appear in the surrounding four cells.
Quadratics: Of the four digits on a circle, two of them are the two solutions of X^2 - aX + b = 0, where a and b are the other two digits on that circle. If the equation has only one solution, that digit occurs twice.
Click here to start the puzzle
Solution code: Row 9.
Comments
on 24. February 2026, 14:29 by bboom
Absolutely impressive that you created this, but honestly it wasn't a great puzzle to solve. For me it basically came down to brute forcing a list of valid quads, and then just crossing off the options for each location, which felt mostly time-consuming rather than hard.
on 24. February 2026, 13:54 by Franjo
I needed some preparation on paper, but then got into a nice flow… Thank you very much for creating and sharing this great math-puzzle.
on 24. February 2026, 07:36 by VolpeRosso
Haha - a very fun puzzle for those quadratically inclined. But... just when one has solved all the equations, and done most of the sudoku... and you're barelling towards the end... There's that sting in the tail! <3
on 24. February 2026, 03:33 by mbumbee
Lovely!! This puzzle isn't for everyone, but that should be clear from the very beginning - and if it's not for you it's ok to move on!
on 23. February 2026, 23:40 by Myxo
Lovely! And with the right math tricks, no notes are needed :)
on 23. February 2026, 23:37 by QuiltyAsCharged
Finish your maths homework first, then you can play your puzzle game!
on 23. February 2026, 23:36 by Fool on Hill
Excellent puzzle. But no way is this 4/5. I did need to do some initial thinking, but after that it solved like a dream with no issues until a slightly technical (perhaps 3/5) ending. I was amazed that it did solve - I am sure there are some uniqueness points buried in there (at least 8 different digits have to be on circles, otherwise there are two you can't distinguish), but that thinking did not cross my mind till I'd solved it.
on 23. February 2026, 15:53 by Yann
Funny, thanks !
on 23. February 2026, 13:55 by Mennoo_
Very interesting concept for a puzzle.
I think the puzzle really requires a page for notes. But with that a loveky solve. Nice setting as well! Loved that
