XYZWing

The XYZWing is very simular to the XYWing technique.
In the example below a XYZWing is explained. Cells A, B and C mark the XYZWing pattern. What we are going to
prove is that the blue mark cell cannot contain the value 9.
The easiest way to se this is to prove that wichever value cell B has, the blue marked cells cannot
have the value 9.
When cell B has the value 1, cell A must have the value 9 and therefore the blue cell cannot have value 9.
When cell B has the value 2, cell C must have the value 9 and therefore the blue cell cannot have value 9.
When cell B has the value 9, the blue cell cannot have value 9.
When we simplify this we can say that wichever value cell B has, the blue cell cannot have value 9. Because of this, we
can say that the blue cell can not be a 9. This candidate value can be removed.


