The New Sudoku Players' Forum

[sebyastiens]

Hello,

I solved both of these with trials & errors at that stage (see screenshot) but I was wondering if there is a technique I could have used before using trial & error process.

I only know X wing, swordfish, unique rectangle and XY wing which I didn't find the possibility to apply at that stage.

Thanks for your help

[dxSudoku]

Here are the two hard steps:
Hidden Rectangle: 3/5 in r4c69,r6c69 => r6c9<>5
XY-Chain: 7 7- r1c6 -6- r1c3 -4- r8c3 -5- r9c2 -4- r9c9 -7 => r1c9<>7

After these it's bunch of Naked and Hidden Singles.

[Wepwawet]

Well, you can start by eliminating the 6 from r4c9, and if you are familiar with Unique Rectangles, then you will be aware of Hidden Rectangles: 3/5 in r4c69 and r6c69 leading to the elimination of 5 from r6c9.

An XY Chain and a W-Wing would see you home and dry, but I don't know if you are familiar with these.
Alternatively, by contradiction the 3 at r6c9 can be eliminated, as it leads to there being two 4's in row 5, and without the 3 in r6c9, it is plain sailing all the way home.
Hope that helps!