Life In 19x19

Your move is very obviously ko. Cool! thanks for letting me know.

If you can't read that out, do easier problems. You're right. These problems are beyond my level. I am around 20 kyu but these problems are for above 15 kyu. However, so far, I have learned two things from asking these hard ...

Level 2 (15 kyu - 5 kyu), Problem 38

Why is S18 wrong? How can white survive? How can white kill black? How can white cause seki?

$$c Level 2 (15k-5k), Problem 38.
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$$ | . . . . . . . . . . . . . . O X X O . |
$$ | . . . . . . . . . . . . . . O X . Z O ...

tekesta wrote:The other two options make a dead shape. Some 4 space shapes can be killed by throwing in.

Ah, I can see it now. Black needs to be able to survive if white makes the first move after seki. If black can't survive, it's not really seki and black just loses. (Hopefully that makes sense...) Thanks!

Level 2 (15 kyu - 5 kyu), Problem 4

koreanproblemacademy-2-4.JPG
http://www.lifein19x19.com/forum/download/file.php?id=3511

I assume this ends in seki if black is to live. My question is, why is O19 so special? Doesn't seki occur with black moving on O18 or R18 as well?

And why doesn't my SGF ...