Thanks for explaining. I was indeed making a logic error. Mentally I had put parentheses around e3 and e4 - doing their subtraction first and then subtracting that result from 0. I used to know that subtraction is not commutative. Funny how my old brain can get stuck on such a simple thing.

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nashvillebudd wrote:

This puzzle seems unsolvable to me.

I start by filling in the givens...d1, c5, e5.

Now looking at column d, d2 cannot be zero since that would force c2 to also be zero, d4 cannot be zero since either b4/c4 must be a zero, and d5 cannot be zero since either a5/b5 must be zero.

That leaves only d3 to be a zero.

But in order for that clusters subtraction to equal zero that would force e3 and e4 to be the same number.

Stalemate.

What am I missing? Can anyone help?

You are reasoning wrongly because when you have negative numbers in a puzzle like this not necessarily e3 and e4 must be the same number, What about a -1 and a 1, for instance?: 0 - (-1) - 1 = 0

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I start by filling in the givens...d1, c5, e5.

Now looking at column d, d2 cannot be zero since that would force c2 to also be zero, d4 cannot be zero since either b4/c4 must be a zero, and d5 cannot be zero since either a5/b5 must be zero.

That leaves only d3 to be a zero.

But in order for that clusters subtraction to equal zero that would force e3 and e4 to be the same number.

Stalemate.

What am I missing? Can anyone help?

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pnm wrote:

I'm thinking probably a volume V before the end of the year..

Sounds like a plan!

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marblevolcano wrote:

FINALLY! I solved A2V1 by figuring out the proper combination in the top right 1- cage.

What a relief that is... but now I have no unsolved book puzzles... I guess I need a new book. What a

I'm thinking probably a volume V before the end of the year..

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This puzzle is a good example to show the benefit of finding cages that can be added and that it is worth looking for the less obvious cells that can be added. Don't just look for the easy options, the central 3x3 group might not look helpful at first, but good progress can be made by adding the cages in that central group, and the lower 2 rows are very helpful even though it might not look like it.

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beaker wrote:

You are talking about the more difficult of the 2 as I spent almost an hour and finally gave up on it!

Yes, the Difficult Killer Sudoku. Thankfully, you are allowed two days to submit, otherwise I would have broken my streak of year to date puzzles. I've changed the title of the thread.

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I could not do it analytically.

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mparisi wrote:

... has a very pleasing symmetry. Was this a hand-generated puzzle?

No, it's just that the puzzle generator has become sentient

(advances in AI these days )

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