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F.E....can you solve it?
Jackson0423   0
an hour ago
Find all functions \( f : \mathbb{R} \to \mathbb{R} \) such that
\[
f\left(\frac{x^2 - f(x)}{f(x) - 1}\right) = x
\]for all real numbers \( x \) satisfying \( f(x) \neq 1 \).
0 replies
Jackson0423
an hour ago
0 replies
Functional equation
Math-wiz   25
N an hour ago by Adywastaken
Source: IMOC SL A1
Find all functions $f:\mathbb{R}\to\mathbb{R}$ such that for all $x,y\in\mathbb{R}$,
$$f(xy+f(x))=f(xf(y))+x$$
25 replies
Math-wiz
Dec 15, 2019
Adywastaken
an hour ago
Nice numer theory
GeoArt   5
N 2 hours ago by Primeniyazidayi
$p$ is a prime number, $m, x, y$ are natural numbers ($m, x, y > 1$). It is known that $\frac{x^p + y^p}{2}$ $=$ $(\frac{x+y}{2} )^m$. Prove that $p = m$.
5 replies
GeoArt
Jan 7, 2021
Primeniyazidayi
2 hours ago
Prove XBY equal to angle C
nataliaonline75   2
N 2 hours ago by starchan
Let $M$ be the midpoint of $BC$ on triangle $ABC$. Point $X$ lies on segment $AC$ such that $AX=BX$ and $Y$ on line $AM$ such that $XY//AB$. Prove that $\angle XBY = \angle ACB$.
2 replies
nataliaonline75
Yesterday at 2:47 PM
starchan
2 hours ago
Unique number to make a square of a rational
Zavyk09   2
N 2 hours ago by Zavyk09
Source: Homework
Find all positive integers $n$ there exists a unique positive integers $m$ such that $\frac{n+m}{m}$ is a square of a rational number.
2 replies
Zavyk09
3 hours ago
Zavyk09
2 hours ago
Classical NT using modular arithmetic
electrovector   7
N 2 hours ago by Blackbeam999
Source: 2022 Turkey TST P1 Day 1 + 2023 Dutch BxMO TST, Problem 5
Find all pairs of prime numbers $(p,q)$ for which
\[2^p = 2^{q-2} + q!.\]
7 replies
electrovector
Mar 13, 2022
Blackbeam999
2 hours ago
Inequality
lgx57   9
N 2 hours ago by lgx57
Source: Own
$a,b,c>0,ab+bc+ca=1$. Prove that

$$\sum \sqrt{8ab+1} \ge 5$$
(I don't know whether the equality holds)
9 replies
lgx57
Saturday at 3:14 PM
lgx57
2 hours ago
old one but good one
Sunjee   2
N 2 hours ago by ehuseyinyigit
If $x_1,x_2,...,x_n $ are positive numbers, then prove that
$$\frac{x_1}{1+x_1^2}+\frac{x_2}{1+x_1^2+x_2^2}+\cdots+ \frac{x_n}{1+x_1^2+\cdots+x_n^2}\geq \sqrt{n}$$
2 replies
Sunjee
4 hours ago
ehuseyinyigit
2 hours ago
Inspired by giangtruong13
sqing   0
3 hours ago
Source: Own
Let $ a,b>0  .$ Prove that$$ \frac{a}{b}+\frac{b}{a}+\frac{a^3}{2b^3+kab^2}+\frac{2b^3}{a^3+b^3+kab^2} \geq \frac{2k+7}{k+2}$$Where $ k\geq 0. $
0 replies
sqing
3 hours ago
0 replies
we can find one pair of a boy and a girl
orl   18
N 3 hours ago by bin_sherlo
Source: Vietnam TST 2001 for the 42th IMO, problem 3
Some club has 42 members. It’s known that among 31 arbitrary club members, we can find one pair of a boy and a girl that they know each other. Show that from club members we can choose 12 pairs of knowing each other boys and girls.
18 replies
orl
Jun 26, 2005
bin_sherlo
3 hours ago
a