Even So

Problem | Solution | Printable page |
Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Find some triples of whole numbers $ a $, $ b $ and $ c $ such that $ a^2 + b^2 + c^2 $ is a multiple of 4. Is it necessarily the case that $ a $, $ b $ and $ c $ must all be even? If so, can you explain why?

Published November 2001.