Something weird with this one FE in integers (probably challenging, maybe not)
by Gaunter_O_Dim_of_math, May 13, 2025, 8:10 PM
During FE problems' solving I found a very specific one:
Find all such f that f: Z -> Z and for all integers a, b, c
f(a^3 + b^3 + c^3) = f(a)^3 + f(b)^3 + f(c)^3.
Everything what I've got is that f is odd, f(n) = n or -n or 0
for all n from 0 to 11 (just bash it), but it is very simple and do not give the main idea.
I actually have spent not so much time on this problem, but definitely have no clue. As far as I see, number theory here or classical FE solving or advanced methods, which I know, do not work at all.
Is here a normal solution (I mean, without bashing and something with a huge number of ugly and weird inequalities)?
Or this is kind of rubbish, which was put just for bash?
Find all such f that f: Z -> Z and for all integers a, b, c
f(a^3 + b^3 + c^3) = f(a)^3 + f(b)^3 + f(c)^3.
Everything what I've got is that f is odd, f(n) = n or -n or 0
for all n from 0 to 11 (just bash it), but it is very simple and do not give the main idea.
I actually have spent not so much time on this problem, but definitely have no clue. As far as I see, number theory here or classical FE solving or advanced methods, which I know, do not work at all.
Is here a normal solution (I mean, without bashing and something with a huge number of ugly and weird inequalities)?
Or this is kind of rubbish, which was put just for bash?
This post has been edited 1 time. Last edited by Gaunter_O_Dim_of_math, Yesterday at 8:30 PM
Reason: one mistake
Reason: one mistake
Cyclic inequality with rational functions
by MathMystic33, May 13, 2025, 6:00 PM
Let
be positive real numbers. Prove the inequality
![\[
\frac{x_1 + 3x_2}{x_2 + x_3}
\;+\;
\frac{x_2 + 3x_3}{x_3 + x_4}
\;+\;
\frac{x_3 + 3x_4}{x_4 + x_1}
\;+\;
\frac{x_4 + 3x_1}{x_1 + x_2}
\;\ge\;8.
\]](//latex.artofproblemsolving.com/5/c/0/5c062a37f6ff120232ae87eb0093a4ce73ee0eb1.png)

![\[
\frac{x_1 + 3x_2}{x_2 + x_3}
\;+\;
\frac{x_2 + 3x_3}{x_3 + x_4}
\;+\;
\frac{x_3 + 3x_4}{x_4 + x_1}
\;+\;
\frac{x_4 + 3x_1}{x_1 + x_2}
\;\ge\;8.
\]](http://latex.artofproblemsolving.com/5/c/0/5c062a37f6ff120232ae87eb0093a4ce73ee0eb1.png)
I got stuck in this combinatorics
by artjustinhere237, May 13, 2025, 4:56 PM
Let
, where
is a positive integer.
Prove that there exists a subset of
with exactly
elements such that the sum of its elements is a prime number.


Prove that there exists a subset of


forced vertices in graphs
by Davdav1232, May 8, 2025, 8:27 PM
Let
be a graph colored using
colors. We say that a vertex is forced if it has neighbors in all the other
colors.
Prove that for any
-regular graph
, there exists a coloring using
colors such that at least
of the colors have a forced vertex of that color.
Note: The graph coloring must be valid, this means no
vertices of the same color may be adjacent.



Prove that for any




Note: The graph coloring must be valid, this means no

Inequality
by nguyentlauv, May 6, 2025, 12:19 PM
Brazilian Locus
by kraDracsO, Sep 9, 2023, 4:45 PM
Let
and
be two fixed points in the plane. For each point
of the plane, outside of the line
, let
be the barycenter of the triangle
. Determine the locus of points
such that
.
Note: The locus is the set of all points of the plane that satisfies the property.








Note: The locus is the set of all points of the plane that satisfies the property.
d1-d2 divides n for all divisors d1, d2
by a_507_bc, May 20, 2023, 4:34 PM
Determine all natural numbers
with at most four natural divisors, which have the property that for any two distinct proper divisors
and
of
, the positive integer
divides
.






P (x^2) = P (x) P (x + 2) for any complex x
by parmenides51, Jul 24, 2021, 8:24 PM
Find all polynomials
with complex coefficients such that
for any complex number 



"Where wisdom and valor fail, all that remains is faith. . . And it can overcome all." -Toa Mata Tahu
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