dailysudoku.com

[George Woods]

Once again a solution, but what is the "official" way of dong it?

initial work leads to
701 000 030
063 418 097
900 307 001

859 720 300
607 580 902
402 006 785

106 800 003
378 645 129
090 000 608

The hint given is 6 at r1c9, OR this can be restated as not 4 at this position

so if we postulate a 4 here, then the position of the 4 in box 9 is revealed

similarly via the hidden pair 56 in row 3 the position of the 4 in box1 is deduced and hence position of 4 in box7

Row 7 now has two 4's which is not allowed hence r1c9 cannot be 4 so must be 6 .... and so on .....

I have serached for x wings xy wings and DRs - don't know any other "formal" techniques, but clearly I have missed something simple, or the draw program is getting more advanced!

[TKiel]

George,

There is a naked triple in row three (4,5,6). After these exclusions, there is an X-wing on 4's that makes 6 the only candidate in r1c9.

[George Woods]

Thanks - I, like others in the same position of being lost, feel like an idiot since my solution embodied pretty much what you have explained!!!!!