Author Archives: kevin

Algebra Challenge – 2025/10/09

For number pairs $(r_i, c_i)$, $i=1,2,…,n$, where $n\ge 1$, $r_i\ge 0$ and $c_i\ge 0$, they have the following property:$$\sum_{i=1}^{n}r_i=\sum_{i=1}^{n}c_i=n^2$$ Additionally, there exists a positive value of $k$ so that for every $i$ value,$i=1,2,…,n$, the following three inequalities hold:$$r_i\le \dfrac{n^3}{k}\ \ … Continue reading

Posted in Algebra | Comments Off on Algebra Challenge – 2025/10/09

USAMTS 5/2/36

Prove that there is no polynomial $P(x)$ with integer coefficients such that $$P(\sqrt[3]{5}+\sqrt[3]{25})=2\sqrt[3]{5}+3\sqrt[3]{25}$$🔑 Proof: Assume that there is a polynomial $P(x)$ of degree $n$, with integer coefficients, and without trivial root of $0$, such that$$P(\sqrt[3]{5}+\sqrt[3]{25})=2\sqrt[3]{5}+3\sqrt[3]{25}$$Therefore, $P(x)$ can be expressed as … Continue reading

Posted in Algebra | Comments Off on USAMTS 5/2/36

USAMTS 4/1/36

During a lecture, each of  mathematicians falls asleep exactly once, and stays asleep for a nonzero amount of time. Each mathematician is awake at the moment the lecture starts, and the moment the lecture finishes. Prove that there are either  mathematicians such … Continue reading

Posted in Algebra, Combinatorics | Comments Off on USAMTS 4/1/36

Count Friends at a Party

You are invited by a host at a party with a total of $2025$ people, including the host. Every pair of two people at the party have exactly one common friend. Among them, what is the maximum and minimum number … Continue reading

Posted in Graph Theory | Comments Off on Count Friends at a Party

Hyperbolas Covered by a Quadrilateral

Four points $A$, $B$, $C$ and $D$ are chosen on each of $4$ hyperbola branches of $x^2y^2=1$ (as $y=\dfrac{1}{x}$ and $y=-\dfrac{1}{x}$ combined). Find the minimum area of the quadrilateral.🔑 Solution: Given that all 4 vertices of the quadrilaterial are on the $4$ branches, let … Continue reading

Posted in Algebra, Calculus, Geometry | Comments Off on Hyperbolas Covered by a Quadrilateral