Practise: X-Chain
This verified teaching position begins directly with a real X-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
Choose one digit and mark units where it has exactly two possible cells. Those are your strong links. Join them with weak links only where two candidates see each other, and alternate the link types. After an odd number of links, check whether an outside candidate sees both endpoints; only those common peers are valid eliminations.
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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