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2023 Official Mock NAIME #15 f(f(f(x))) = f(f(x))
parmenides51   3
N 5 hours ago by jasperE3
How many non-bijective functions $f$ exist that satisfy $f(f(f(x))) = f(f(x))$ for all real $x$ and the domain of f is strictly within the set of $\{1,2,3,5,6,7,9\}$, the range being $\{1,2,4,6,7,8,9\}$?

Even though this is an AIME problem, a proof is mandatory for full credit. Constants must be ignored as we dont want an infinite number of solutions.
3 replies
parmenides51
Dec 4, 2023
jasperE3
5 hours ago
Geometry
AlexCenteno2007   3
N Today at 4:18 PM by AlexCenteno2007
Let ABC be an acute triangle and let D, E and F be the feet of the altitudes from A, B and C respectively. The straight line EF and the circumcircle of ABC intersect at P such that F is between E and P, the straight lines BP and DF intersect at Q. Show that if ED = EP then CQ and DP are parallel.
3 replies
AlexCenteno2007
Apr 28, 2025
AlexCenteno2007
Today at 4:18 PM
Cube Sphere
vanstraelen   4
N Today at 2:37 PM by pieMax2713

Given the cube $\left(\begin{array}{ll} EFGH \\ ABCD \end{array}\right)$ with edge $6$ cm.
Find the volume of the sphere passing through $A,B,C,D$ and tangent to the plane $(EFGH)$.
4 replies
vanstraelen
Today at 1:10 PM
pieMax2713
Today at 2:37 PM
Square number
linkxink0603   3
N Today at 2:36 PM by Zok_G8D
Find m is positive interger such that m^4+3^m is square number
3 replies
linkxink0603
Today at 11:20 AM
Zok_G8D
Today at 2:36 PM
Combinatorics
AlexCenteno2007   0
Today at 2:05 PM
Adrian and Bertrand take turns as follows: Adrian starts with a pile of ($n\geq 3$) stones. On their turn, each player must divide a pile. The player who can make all piles have at most 2 stones wins. Depending on n, determine which player has a winning strategy.
0 replies
AlexCenteno2007
Today at 2:05 PM
0 replies
How many pairs
Ecrin_eren   6
N Today at 12:57 PM by Ecrin_eren


Let n be a natural number and p be a prime number. How many different pairs (n, p) satisfy the equation:

p + 2^p + 3 = n^2 ?



6 replies
Ecrin_eren
May 2, 2025
Ecrin_eren
Today at 12:57 PM
parallelogram in a tetrahedron
vanstraelen   1
N Today at 12:19 PM by vanstraelen
Given a tetrahedron $ABCD$ and a plane $\mu$, parallel with the edges $AC$ and $BD$.
$AB \cap \mu=P$.
a) Prove: the intersection of the tetrahedron with the plane is a parallelogram.
b) If $\left|AC\right|=14,\left|BD\right|=7$ and $\frac{\left|PA\right|}{\left|PB\right|}=\frac{3}{4}$,
calculates the lenghts of the sides of this parallelogram.
1 reply
vanstraelen
May 5, 2025
vanstraelen
Today at 12:19 PM
Find max
tranlenhanhbnd   0
Today at 11:50 AM
Let $x,y,z>0$ and $x^2+y^2+z^2=1$. Find max
$D=\dfrac{x}{\sqrt{2 y z+1}}+\dfrac{y}{\sqrt{2 z x+1}}+\dfrac{z}{\sqrt{2 x y+1}}$.
0 replies
tranlenhanhbnd
Today at 11:50 AM
0 replies
triangle ABC, # BCDE, BE//AM, BE=AM/2, midpoint (Greece Junior 2014)
parmenides51   8
N Today at 10:35 AM by AylyGayypow009
Let $ABC$ be a triangle and let $M$ be the midpoint $BC$. On the exterior of the triangle, consider the parallelogram $BCDE$ such that $BE//AM$ and $BE=AM/2$ . Prove that line $EM$ passes through the midpoint of segment $AD$.
8 replies
parmenides51
Jul 14, 2019
AylyGayypow009
Today at 10:35 AM
a,b,c irrational, f(x)=ax^2+bx+c : [-1,1] to [-1,1] surjective
tom-nowy   1
N Today at 10:27 AM by alexheinis
Consider a quadratic function $f(x) = ax^2 + bx + c$, where the coefficients $a, b,$ and $c$ are all irrational numbers.
Is it possible for this function to have a maximum value of $1$ and a minimum value of $-1$ over the interval $[-1, 1]$?
1 reply
tom-nowy
Yesterday at 11:03 PM
alexheinis
Today at 10:27 AM
a