Y by OronSH, MarkBcc168, Rounak_iitr, Sedro
Let
be the set of real numbers. Let
be a function such that
for every
. Assume that the inequality is strict for some
.
Prove that either
for every
or
for every
.


![\[f(x+y)f(x-y)\geqslant f(x)^2-f(y)^2\]](http://latex.artofproblemsolving.com/5/d/3/5d3476fd9195d085d0030d6036a9fde1cf6756a7.png)


Prove that either




This post has been edited 2 times. Last edited by peace09, Jul 17, 2024, 12:27 PM