by Animator » Sun May 22, 2005 11:56 am
Ok,
Let's first look at the starting point.
Possibilities for row 6:
r6c1: 3, 6, 7, 9
r6c3: 3, 5, 7
r6c6: 6, 9
r6c7: 5, 7, 9
r6c8: 6, 7, 9
Now, when you follow all steps I previously explained, then you will be able to remove the number 7 as a candidate for r6c8:
Row6: (after excluding 7)
r6c1: 3, 6, 7, 9
r6c3: 3, 5, 7
r6c6: 6, 9
r6c7: 5, 7, 9
r6c8: 6, 9
Now you see that r6c6 and r6c8 has to have a 6 or a 9, if you fill in a 6 or a 9 in any other place in the row then you cannot finish the grid... (you will either end up with two cells that can only be 6, or two cells that has 9 as only candidate, both are incorrect).