Equations

by Jackson0423, Apr 22, 2025, 4:36 PM

Solve the system of equations
\[
\begin{cases}
x - y z = 1,\\[2pt]
y - z x = 2,\\[2pt]
z - x y = 4.
\end{cases}
\]

2016 Kmo Final round

by Jackson0423, Apr 22, 2025, 3:58 PM

Let \(x,y,z\in\mathbb R\) with \(x^{2}+y^{2}+z^{2}=1\).
Find the maximum value of
\[
(x^{2}-yz)(y^{2}-zx)(z^{2}-xy).
\]

2^x+3^x = yx^2

by truongphatt2668, Apr 22, 2025, 3:38 PM

Prove that the following equation has infinite integer solutions:
$$2^x+3^x = yx^2$$

Integer representation

by RL_parkgong_0106, Apr 22, 2025, 2:23 PM

Show that for any positive integer $n$, there exists some positive integer $k$ that makes the following equation have no integer root $(x_1, x_2, x_3, \dots, x_n)$.

$$x_1^{2^1}+x_2^{2^2}+x_3^{2^3}+\dots+x_n^{2^n}=k$$

A cyclic inequality

by KhuongTrang, Apr 21, 2025, 4:18 PM

https://scontent.fsgn8-3.fna.fbcdn.net/v/t39.30808-6/492231047_688189297700214_244542319935452144_n.jpg?_nc_cat=100&ccb=1-7&_nc_sid=127cfc&_nc_ohc=xQijXmYebS4Q7kNvwFGnEsJ&_nc_oc=AdnkURNB_TMHGDtMopGwGHIze5ttpMfPlG6_IvyiEtuBvsrjxmHu2ER5OMaRWyfSq1oAwajVe1_upssAjnhpMkCO&_nc_zt=23&_nc_ht=scontent.fsgn8-3.fna&_nc_gid=NwcFC-jSTnopA34ZcTHl0Q&oh=00_AfEX7I6TDrNddWcG3dW1-eKfIW1nhr5kYROU6TEFmN56kg&oe=680C389C
https://cms.math.ca/.../uploads/2025/04/Wholeissue_51_4.pdf

Iran second round 2025-q1

by mohsen, Apr 19, 2025, 10:21 AM

Find all positive integers n>2 such that sum of n and any of its prime divisors is a perfect square.

FE solution too simple?

by Yiyj1, Apr 9, 2025, 3:26 AM

Find all functions $f: \mathbb{R} \rightarrow \mathbb{R}$ such that the equality $$f(f(x)+y) = f(x^2-y)+4f(x)y$$holds for all pairs of real numbers $(x,y)$.

My solution

I feel like my solution is too simple. Is there something I did wrong or something I missed?

hard problem

by Cobedangiu, Apr 2, 2025, 6:11 PM

Let $x,y,z>0$ and $xy+yz+zx=3$ : Prove that :
$\sum  \ \frac{x}{y+z}\ge\sum  \frac{1}{\sqrt{x+3}}$

Factor sums of integers

by Aopamy, Feb 23, 2023, 3:13 AM

Let $n$ be a positive integer. A positive integer $k$ is called a benefactor of $n$ if the positive divisors of $k$ can be partitioned into two sets $A$ and $B$ such that $n$ is equal to the sum of elements in $A$ minus the sum of the elements in $B$. Note that $A$ or $B$ could be empty, and that the sum of the elements of the empty set is $0$.

For example, $15$ is a benefactor of $18$ because $1+5+15-3=18$.

Show that every positive integer $n$ has at least $2023$ benefactors.

Factor of P(x)

by Brut3Forc3, Apr 4, 2010, 2:45 AM

If $ P(x),Q(x),R(x)$, and $ S(x)$ are all polynomials such that \[ P(x^5)+xQ(x^5)+x^2R(x^5)=(x^4+x^3+x^2+x+1)S(x),\] prove that $ x-1$ is a factor of $ P(x)$.

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