Timeline for Convex upper bound on a linear-fractional function

8 events

when toggle format	what		by	license	comment
Dec 7, 2012 at 5:23	history	edited	Norouzi	CC BY-SA 3.0	edited title
Dec 6, 2012 at 16:29	answer	added	Norouzi		timeline score: 1
Dec 6, 2012 at 16:19	history	edited	Norouzi	CC BY-SA 3.0	added 106 characters in body
Dec 6, 2012 at 8:38	answer	added	Pietro Majer		timeline score: 1
Dec 6, 2012 at 3:17	comment	added	Norouzi		The function f is quasiliner. It has convex parts eg. when one sets $x=1$ and only varies $y$, $f(x,y) = f(y) = \frac{1}{c+y}$, and concave parts, eg. when one sets $y = x$, and so $f(x,y) = f(x) = \frac{x}{c+x}$. I would like to find a convex upper-bound for $f$ if possible.
Dec 6, 2012 at 1:53	comment	added	fedja		Let's first make sure that we speak the same language: "convex" means $f(\frac{a+b}2)\le\frac{f(a)+f(b)}2$. Are you sure that you mean this and not the opposite inequality, which I would normally call "concavity"?
Dec 6, 2012 at 0:07	history	edited	Norouzi	CC BY-SA 3.0	deleted 9 characters in body
Dec 5, 2012 at 23:18	history	asked	Norouzi	CC BY-SA 3.0