Practise: XY-Chain
This verified teaching position begins directly with a real XY-Chain pattern. Follow the chain, inspect the candidates and make the deduction before you continue.
You are at the verified key position. Use a hint to follow the chain link by link when you need support.
Your turn first
Spot the idea before the hint explains it
- 1. Look
- 2. Check
- 3. Proof
Look at the marked starting cells and their candidates. Which digit or candidate relation is forced, and what visible row, column or box fact supports your idea?
How to spot it
Start with a bi-value cell and follow matching candidates through other bi-value cells that see the preceding cell. Keep the links alternating and look for a chain whose endpoints share a candidate. That endpoint candidate can be eliminated only from cells seeing both ends.
Put it to use
Where you will meet it
Expert grids are the only place this pattern regularly decides the solve. Bring your notes.
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