Beginner Exercise 148 / Solution

Sub-page of BeginnerExercise148
Black to play.  

After B1, White is left without two eyes.

B1 threatens to capture the three white stones to the left of B1. White can not form two eyes without these stones. White must connect these stones to the rest of the White group using a or prevent Black from capturing these stones by playing W2, which makes a Black attempt to capture the stones by playing at a a self-atari.

Unfortunately for White, neither White a nor W2 make life. W2 threatens to make a second eye with W3, but B3 prevents that.

The key to the problem is the first rule of killing groups: Examine a play at the eye-point.

Bill: No, that's the third rule for killing groups. The first rule is to reduce the space for making eyes. See Hane, Cut, Placement.

Black failure  

Brent: For a while I had convinced myself that B1 worked as well, but then realized that it doesn't, so I thought I'd add a failure diagram to show why. After B1 White cannot connect at a because of shortage of liberties. However, W2 solves White's problems. White threatens to now connect at a and live, so...

Black failure, continued  

...Black must capture there instead. But now White plays W4 and lives: playing at b in an attempt to falsily an eye would be auto-atari for Black. So Black must connect out first, giving White the chance to play at b and solidify the second eye.

White failure  

unkx80: W2 doesn't solve the problem, B3 kills. After which, a and b are miai.

White lives  

However, W2 lives.


W4 at white+circle.

Bill: Now if Black plays B1 in an attempt to take away White's eye at a, W2 - W4 captures Black's stones with a snapback.

Brent: Oops. Looks like I was right but for the wrong reason. (= Thanks.

White lives  

This also works. Therefore, by "problem principles" alone, one can deduce that the correct solution is at the other key point. ilan

Black kills,no analysis required  
Does not work either.  

Unfortunately, this does not work either. --unkx80

Ooops, forgot about the right hand side. I die an ignominious death. ilan

Beginner Exercise 148 / Solution last edited by on April 22, 2009 - 22:52
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