The way I understand A4 is that it says “if moving by Δ is good, then moving by any fraction λΔ is also good”.
And A5 says “if moving by Δ is good, then moving by any multiple nΔ is also good”, which is much stronger.
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.
The way I understand A4 is that it says “if moving by Δ is good, then moving by any fraction λΔ is also good”.
And A5 says “if moving by Δ is good, then moving by any multiple nΔ is also good”, which is much stronger.
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.