[bubblyworld]

Right, I agree that they are semidecidable, thanks for clarifying. My interpretation of "only x=0 is undecidable" was that you were claiming the other two were decidable (which is a reasonable reading imo). But it sounds like we don't actually disagree here.

[lisper]

It's my fault for not being more explicit. I just didn't think it all the way through.