Your understanding of A4 is right. In A5, “good” should be replaced with “bad.”
(and everywhere you say “good” and “bad”, they are the non-strict versions of the words)
yep!
Okay, I now think A5 implies: “if moving by Δ is good, then moving by any negative multiple −nΔ is bad”. Which checks out to me re concavity.
Your understanding of A4 is right. In A5, “good” should be replaced with “bad.”
(and everywhere you say “good” and “bad”, they are the non-strict versions of the words)
yep!
Okay, I now think A5 implies: “if moving by Δ is good, then moving by any negative multiple −nΔ is bad”. Which checks out to me re concavity.