Given two primes $p$ and $q$, is $v_p(q^n+n^q)$ unbounded as $n$ varies? (Proposed by Ivan Chan Kai Chin)
2025 Malaysian IMO Training Camp
BIMO 1 Christmas Test
December 25, 2024
There are $2024$ points on a circle. A purple elephant labels the points $P_1,P_2,\ldots,P_{2024}$ in some order, and walks along the points from $P_1$ to $P_{2024}$ in this order, while laying some eggs. To ensure the elephant does not step on the eggs it laid, the chords $P_1P_2, P_2P_3, \ldots, P_{2023}P_{2024}$ must not intersect each other except possibly at their endpoints. How many labellings are there? (Note: Two labellings are the same if one is a rotation of the other.) (Proposed by Ho Janson)
Given a triangle $ABC$ with $M$ the midpoint of minor arc $BC$. Let $H$ be the feet of altitude from $A$ to $BC$. Let $S$ and $T$ be the reflections of $B$ and $C$ with respect to line $AM$. Suppose the circle $(HST)$ meets $BC$ again at a point $P$. Prove that $\angle AMP = 90^\circ$. (Proposed by Tan Rui Xuen)
Find all functions $f:\mathbb R\to\mathbb R$ such that \[f(x^2)+2xf(y)=yf(x)+xf(x+y).\] (Proposed by Yeoh Yi Shuen)
Let $n$ be an odd positive integer. There is a graph $G$ with $2n$ vertices such that if you partition the vertices into two groups $A$ and $B$ with $n$ vertices each, then the subgraph consisting of only vertices and edges within $A$ is connected and has a closed path containing all of its edges, starting and ending with the same vertex. The same condition is true for $B$ as well. Is $G$ necessarily a clique? (Proposed by Ho Janson)
Let $a_1, a_2, \ldots, a_{2024}$ be positive integers such that $a_{i+1}+1$ is a multiple of $a_i$ for all $i = 1, 2, \ldots , 2024$, with indices taken modulo $2024$. Find the maximum possible value of $a_1 + a_2 + \ldots + a_{2024}$. (Proposed by Ivan Chan Guan Yu)
Let $n$ be a positive integer and $a_1\le a_2\le\ldots\le a_{n+1}$ and $b_1\le b_2\le\ldots\le b_n$ be real numbers such that for all $k\le n$, \[\binom nk\sum_{\substack{1\le i_1<i_2<\ldots<i_k\le n+1,\\i_1,i_2,\ldots,i_k\in\mathbb N}}a_{i_1}a_{i_2}\ldots a_{i_k} = \binom{n+1}k\sum_{\substack{1\le j_1<j_2<\ldots<j_k\le n,\\j_1,j_2,\ldots,j_k\in\mathbb N}}b_{j_1}b_{j_2}\ldots b_{j_k}.\]Show that \[a_1\le b_1\le a_2\le b_2\le \ldots \le a_n\le b_n\le a_{n+1}.\] (Proposed by Ivan Chan Guan Yu)
Let $ABC$ be a non-isosceles and acute triangle. $X$ is a point on arc $BC$ not containing $A$ such that $BA-CA = CX-BX$. The incircle of $\triangle ABC$ touches $AC$ and $AB$ at $E$ and $F$ respectively. The $X$-excircle of $\triangle XBC$ touches $XC$ and $XB$ at $Y$ and $Z$ respectively. Let $T$ be such that $TA$ and $TX$ bisects $\angle BAC$ and $\angle BXC$ respectively. Prove that $T$ lies on the radical axis of circles $(BFZ)$ and $(CEY)$. (Proposed by Chuah Jia Herng)
Junior Olympiad of Malaysia 2025
January 19, 2025
Let $ABC$ be a triangle with $AB<AC$ and with its incircle touching the sides $AB$ and $BC$ at $M$ and $J$ respectively. A point $D$ lies on the extension of $AB$ beyond $B$ such that $AD=AC$. Let $O$ be the midpoint of $CD$. Prove that the points $J$, $O$, $M$ are collinear. (Proposed by Tan Rui Xuen)
Determine all infinite sequences of nonnegative integers $a_1,a_2,\ldots$ such that: 1. Every positive integer appears in the sequence at least once, and; 2. $a_i$ is the smallest integer $j$ such that $a_{j+2}=i$, for all $i\ge 1$. (Proposed by Ho Janson)
Minivan and Megavan play a game. For a positive integer $n$, Minivan selects a sequence of integers $a_1,a_2,\ldots,a_n$. An \textit{operation} on $a_1,a_2,\ldots,a_n$ means selecting an $a_i$ and increasing it by $1$. Minivan and Megavan take turns, with Minivan going first. On Minivan's turn, he performs at most $2025$ operations, and he may choose the same integer repeatedly. On Megavan's turn, he performs exactly $1$ operation instead. Megavan wins if at any point in the game, including in the middle of Minivan's operations, two numbers in the sequence are equal. (Proposed by Ho Janson)
For each positive integer $k$, find all positive integer $n$ such that there exists a permutation $a_1,\ldots,a_n$ of $1,2,\ldots,n$ satisfying $$a_1a_2\ldots a_i\equiv i^k \pmod n$$for each $1\le i\le n$. (Proposed by Tan Rui Xuen and Ivan Chan Guan Yu)
Let $ABC$ be a scalene triangle and $I$ be its incenter. Suppose the incircle $\omega$ touches $BC$ at a point $D$, and $N$ lies on $\omega$ such that $ND$ is a diameter of $\omega$. Let $X$ and $Y$ be points on lines $AC$ and $AB$ respectively such that $\angle BIX = \angle CIY = 90^\circ$. Let $V$ be the feet of perpendicular from $I$ onto line $XY$. Prove that the points $I$, $V$, $A$, $N$ are concyclic. (Proposed by Ivan Chan Guan Yu)