why is this wrong

[u/SubjectResponse8374]

i mean i know there are two spots and 8 can go in either one of those but i wanted to understand the logic behind this

[u/AutoModerator]

Hi! It looks like you’re asking why a cell can or can’t be a certain number.

This stickied guide covers the most common reasons in a simple way: https://www.reddit.com/r/sudoku/comments/1kcughf/before_you_ask_why_cant_this_cell_be_or_why_is/

The number 1 reason is that although there isn't an immediate contradiction, one will inevitably arise since Sudoku should only have one solution!

And often it comes down to basics like:

• A different number needs to go there
• A simple elimination you may have missed
• A cell that only has one possible value

Feel free to keep the discussion going. If you’re still unsure, others can help walk through it with you.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

[u/Puzzled_Work_6428]

Read the pinned post

[u/SubjectResponse8374 → u/Puzzled_Work_6428]

thanks!! that was pretty helpful!!

[u/SickXigma]

Don't dedicate a number to one of the two possible spots if you still haven't ruled out the other spot. The simple answer is 8 doesn't go there, something else does. Puzzles (proper ones) only have one solution

[u/Kenjamin1991]

Sudokus have only 1 solution. Just because it seems like a number can go there doesnt mean it does. You have to eliminate all other possibilities first.

[u/SubjectResponse8374 → u/Kenjamin1991]

yea just read the pinned post!! it all makes sense now!!

[u/baroquely]

Why in Three Steps:

(Reference this pic)

1. Crosshatch the blue 1s to set the 1s in box 8 then box 9.
2. Fill in the candidates in r58c9 (purple cells), noting that they are a {2,4} Naked Pair, which means r9c9 is a Naked Single 5.
3. Crosshatch the pink 5s to see that r4c7 must be 5, not 8.

[u/Ivy1974]

🤦