With this solving technique, we will prove the two following assertions:
Each assertion is proved by a chain of simple assertions. The chains may be dynamic, which means that the conclusions of multiple sub-chains are combined.
The details of each chain is given below. Use the view selector below the grid to switch between the graphical illustrations of the two chains.
Chain 1: If A2 contains the value 9, then I8 must contain the value 9 (View 1):
(1) If A2 contains the value 9 then F2 cannot contain the value 9 (the value can occur only once in the row)
(2) If F2 does not contain the value 9 then F2 must contain the value 1 (only remaining potential value in the cell)
(3) If F2 contains the value 1 then F9 cannot contain the value 1 (the value can occur only once in the col)
(4) If A2 contains the value 9 (initial assumption) then B3 cannot contain the value 9 (the value can occur only once in the box)
(5) If B3 does not contain the value 9 then B9 must contain the value 9 (only remaining position in the column)
(6) If B9 contains the value 9 then B9 cannot contain the value 1 (the cell can contain only one value)
(7) If B9 does not contain the value 1 and F9 does not contain the value 1 (3) then C9 must contain the value 1 (only remaining position in the row)
(8) If C9 contains the value 1 then C9 cannot contain the value 8 (the cell can contain only one value)
(9) If B9 contains the value 9 (5) then B9 cannot contain the value 8 (the cell can contain only one value)
(10) If B9 does not contain the value 8 and C9 does not contain the value 8 (8) then G9 must contain the value 8 (only remaining position in the row)
(11) If G9 contains the value 8 then G9 cannot contain the value 6 (the cell can contain only one value)
(12) If G9 does not contain the value 6 then G8 must contain the value 6 (only remaining position in the box)
(13) If G8 contains the value 6 then G8 cannot contain the value 9 (the cell can contain only one value)
(14) If G8 does not contain the value 9 then I8 must contain the value 9 (only remaining position in the box)
Chain 2: If A2 does not contain the value 9, then I8 must contain the value 9 (View 2):
(1) If A2 does not contain the value 9 then B3 must contain the value 9 (only remaining position in the box)
(2) If B3 contains the value 9 then I3 cannot contain the value 9 (the value can occur only once in the row)
(3) If I3 does not contain the value 9 then I8 must contain the value 9 (only remaining position in the column)