Help – Sudoku XY-Wing 

Read the Sudoku help page for the rules, and the techniques potentially required to solve BrainBashers Sudoku.

An XY-Wing is a very advanced technique which can eliminate certain candidates from squares. Its name comes from the pattern formed by the digits and is not related to X-Wing.

We are looking for three squares, each of which contains exactly two digits. The first square contains XY and we require a buddy of this square to contain XZ. We then require another buddy of the XY square to contain YZ.

Any squares that are buddies to both XZ & YZ cannot contain Z. Why? Because it doesn't matter whether the XY is X or Y, the Z will be in either XZ or YZ and hence can be removed from their buddies.