I got this puzzle from a book, I think, but I would be hard-pressed to remember which one. In any case, I believe that it is relatively well-known. Although quite simple, I feel that it has a pleasing air of algebraic mystery about it. I have also found that it is a particularly good question for A-level students to check their understanding of algebra, along with their general problem-solving skills.

**Difficulty: ***

**Maths knowledge required:** GCSE algebra [i.e. 14-16 year olds]. Although KS3 would do….

**Puzzle:**

Simplify this expression:

(*x* − *a*) (*x* − *b*) (*x* − *c*) … (*x* − *z*)

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**Click HERE for the solution.
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**DIFFICULTY RATINGS:
**

*****– Not too taxing

******– Requires significant thought

*******– Extremely difficult

**!!!!**– Requires high level mathematics / Unsolved / Insoluble

Thomas Oléron Evans, 2015