How to write a proof: from (A + B) = C to (A - B) = (C - 2B)

[jgens]

No need to bring any calculus or analysis into this CompuChip. The proof is pretty straight-forward without it. Just note that (2+ε)(2-ε) = 4-ε² ≤ 4 (where -2 ≤ ε ≤ 2) to show that the quadratic is bounded above by 4 on the desired interval.

 

[reenmachine]

No need to bring any calculus or analysis into this CompuChip. The proof is pretty straight-forward without it. Just note that (2+ε)(2-ε) = 4-ε² ≤ 4 (where -2 ≤ ε ≤ 2) to show that the quadratic is bounded above by 4 on the desired interval.

I'm not really sure what you're talking about at the end of your post but perhaps this is similar to what I attempted in my proof (see link in my post above)?