The "Y-Wing" method is similar to the "X-Wing," but it is based on three corners instead of four.
Давайте посмотрим на an example of this method.
To begin, we need to find a cell that has exactly two candidates. We will call this cell the "pivot."
Next, we find two other cells that also have only two candidates. These cells (called "pincers") must be in the same row, column, or block as the "pivot." One of the two numbers in each "pincer" must be the same as one of the numbers in the "pivot." The other number in both "pincers" must be the same.
Now, let's see where the two "pincers" intersect. We see it is the cell in the bottom row. If this cell contains the candidate that is shared by both "pincers," we can eliminate it. In this case, that number is 4, because both "pincers" contain a 4.
Это the principle of the "Y-Wing" solving method. It is an advanced Судоку strategy, and you may need some time and practice to understand it fully.