Olympiad problems

2017 Moldova Team Selection Test, 2

Tags: algebra , polynomial

Let $$f(X)=a_{n}X^{n}+a_{n-1}X^{n-1}+\cdots +a_{1}X+a_{0}$$be a polynomial with real coefficients which satisfies $$a_{n}\geq a_{n-1}\geq \cdots \geq a_{1}\geq a_{0}>0.$$Prove that for every complex root $z$ of this polynomial, we have $|z|\leq 1$.

2010 Thailand Mathematical Olympiad, 9

Tags: polynomial , algebra

Let $a, b, c$ be real numbers so that all roots of the equation $2x^5 + 5x^4 + 5x^3 + ax^2 + bx + c = 0$ are real. Find the smallest real root of the equation above.

2018 Centroamerican and Caribbean Math Olympiad, 5

Tags: algebra , polynomial

Let $n$ be a positive integer, $1<n<2018$. For each $i=1, 2, \ldots ,n$ we define the polynomial $S_i(x)=x^2-2018x+l_i$, where $l_1, l_2, \ldots, l_n$ are distinct positive integers. If the polynomial $S_1(x)+S_2(x)+\cdots+S_n(x)$ has at least an integer root, prove that at least one of the $l_i$ is greater or equal than $2018$.

1976 IMO Longlists, 11

Tags: polynomial , recurrence relation , root , chebyshev polynomial , algebra

Let $P_{1}(x)=x^{2}-2$ and $P_{j}(x)=P_{1}(P_{j-1}(x))$ for j$=2,\ldots$ Prove that for any positive integer n the roots of the equation $P_{n}(x)=x$ are all real and distinct.

2019 Iran Team Selection Test, 4

Tags: algebra , polynomial

Let $1<t<2$ be a real number. Prove that for all sufficiently large positive integers like $d$, there is a monic polynomial $P(x)$ of degree $d$, such that all of its coefficients are either $+1$ or $-1$ and $$\left|P(t)-2019\right| <1.$$ [i]Proposed by Navid Safaei[/i]

2010 Peru IMO TST, 2

Tags: polynomial , number theory , size

A positive integer $N$ is called [i]balanced[/i], if $N=1$ or if $N$ can be written as a product of an even number of not necessarily distinct primes. Given positive integers $a$ and $b$, consider the polynomial $P$ defined by $P(x)=(x+a)(x+b)$. (a) Prove that there exist distinct positive integers $a$ and $b$ such that all the number $P(1)$, $P(2)$,$\ldots$, $P(50)$ are balanced. (b) Prove that if $P(n)$ is balanced for all positive integers $n$, then $a=b$. [i]Proposed by Jorge Tipe, Peru[/i]

2022 Belarusian National Olympiad, 9.8

Tags: algebra , polynomial

Does there exist a polynomial $p(x)$ with integer coefficients for which $$p(\sqrt{2})=\sqrt{2}$$ $$p(2\sqrt{2})=2\sqrt{2}+2$$

2022 ISI Entrance Examination, 4

Tags: polynomial

Let $P(x)$ be an odd degree polynomial in $x$ with real coefficients. Show that the equation $P(P(x))=0$ has at least as many distinct real roots as the equation $P(x)=0$.

2013 Iran MO (3rd Round), 5

Tags: polynomial , trigonometry , complex number , algebra

Prove that there is no polynomial $P \in \mathbb C[x]$ such that set $\left \{ P(z) \; | \; \left | z \right | =1 \right \}$ in complex plane forms a polygon. In other words, a complex polynomial can't map the unit circle to a polygon. (30 points)

2020 Korean MO winter camp, #3

Tags: algebra , polynomial

Find all integer coefficient polynomials $Q$ such that [list] [*] $Q(n)\ge 1$ $\forall n\in \mathbb{Z}_+$. [*] $Q(mn)$ and $Q(m)Q(n)$ have the same number of prime divisors $\forall m,n\in\mathbb{Z}_+$. [/list]

2013 All-Russian Olympiad, 2

Tags: polynomial , algebra

Peter and Vasil together thought of ten 5-degree polynomials. Then, Vasil began calling consecutive natural numbers starting with some natural number. After each called number, Peter chose one of the ten polynomials at random and plugged in the called number. The results were recorded on the board. They eventually form a sequence. After they finished, their sequence was arithmetic. What is the greatest number of numbers that Vasil could have called out? [i]A. Golovanov[/i]

2005 Germany Team Selection Test, 2

Tags: polynomial , function , power of 2 , algebra

For any positive integer $ n$, prove that there exists a polynomial $ P$ of degree $ n$ such that all coeffients of this polynomial $ P$ are integers, and such that the numbers $ P\left(0\right)$, $ P\left(1\right)$, $ P\left(2\right)$, ..., $ P\left(n\right)$ are pairwisely distinct powers of $ 2$.

2019 Middle European Mathematical Olympiad, 2

Tags: algebra , polynomial , root

Let $\alpha$ be a real number. Determine all polynomials $P$ with real coefficients such that $$P(2x+\alpha)\leq (x^{20}+x^{19})P(x)$$ holds for all real numbers $x$. [i]Proposed by Walther Janous, Austria[/i]

2011 Israel National Olympiad, 2

Tags: algebra , root , polynomial , sum of roots

Evaluate the sum $\sqrt{1-\frac{1}{2}\cdot\sqrt{1\cdot3}}+\sqrt{2-\frac{1}{2}\cdot\sqrt{3\cdot5}}+\sqrt{3-\frac{1}{2}\cdot\sqrt{5\cdot7}}+\dots+\sqrt{40-\frac{1}{2}\cdot\sqrt{79\cdot81}}$.

2016 AIME Problems, 11

Tags: polynomial

Let $P(x)$ be a nonzero polynomial such that $(x-1)P(x+1)=(x+2)P(x)$ for every real $x$, and $\left(P(2)\right)^2 = P(3)$. Then $P(\tfrac72)=\tfrac{m}{n}$, where $m$ and $n$ are relatively prime positive integers. Find $m + n$.

2010 Indonesia TST, 1

Tags: polynomial , relatively prime , number theory , algebra

find all pairs of relatively prime natural numbers $ (m,n) $ in such a way that there exists non constant polynomial f satisfying \[ gcd(a+b+1, mf(a)+nf(b) > 1 \] for every natural numbers $ a $ and $ b $

2021 Indonesia TST, A

Tags: algebra , polynomial

Given a polynomial $p(x) =Ax^3+x^2-A$ with $A \neq 0$. Show that for every different real number $a,b,c$, at least one of $ap(b)$, $bp(a)$, and $cp(a)$ not equal to 1.

MathLinks Contest 7th, 5.1

Tags: algebra , polynomial , inequalities , vieta , product of roots , absolute value

Find all real polynomials $ g(x)$ of degree at most $ n \minus{} 3$, $ n\geq 3$, knowing that all the roots of the polynomial $ f(x) \equal{} x^n \plus{} nx^{n \minus{} 1} \plus{} \frac {n(n \minus{} 1)}2 x^{n \minus{} 2} \plus{} g(x)$ are real.

2000 Putnam, 6

Tags: algebra , polynomial , modular arithmetic , induction , rational root theorem , function

Let $f(x)$ be a polynomial with integer coefficients. Define a sequence $a_0, a_1, \cdots $ of integers such that $a_0=0$ and $a_{n+1}=f(a_n)$ for all $n \ge 0$. Prove that if there exists a positive integer $m$ for which $a_m=0$ then either $a_1=0$ or $a_2=0$.

2010 USA Team Selection Test, 1

Tags: number theory , greatest common divisor , algebra , polynomial , modular arithmetic , induction , calculus

Let $P$ be a polynomial with integer coefficients such that $P(0)=0$ and \[\gcd(P(0), P(1), P(2), \ldots ) = 1.\] Show there are infinitely many $n$ such that \[\gcd(P(n)- P(0), P(n+1)-P(1), P(n+2)-P(2), \ldots) = n.\]

2001 Putnam, 3

Tags: algebra , polynomial , quadratic , quadratic formula

For each integer $m$, consider the polynomial \[ P_m(x)=x^4-(2m+4)x^2+(m-2)^2. \] For what values of $m$ is $P_m(x)$ the product of two non-consant polynomials with integer coefficients?

2010 Saint Petersburg Mathematical Olympiad, 3

Tags: algebra , polynomial

$a$ is irrational , but $a$ and $a^3-6a$ are roots of square polynomial with integer coefficients.Find $a$

2005 Greece Team Selection Test, 1

Tags: algebra , polynomial , root

The side lengths of a triangle are the roots of a cubic polynomial with rational coefficients. Prove that the altitudes of this triangle are roots of a polynomial of sixth degree with rational coefficients.

2008 IMC, 3

Tags: algebra , polynomial , quadratic

Let $p$ be a polynomial with integer coeﬃcients and let $a_1<a_2<\cdots <a_k$ be integers. Given that $p(a_i)\ne 0\forall\; i=1,2,\cdots, k$. [list] (a) Prove $\exists\; a\in \mathbb{Z}$ such that \[ p(a_i)\mid p(a)\;\;\forall i=1,2,\dots ,k \] (b) Does there exist $a\in \mathbb{Z}$ such that \[ \prod_{i=1}^{k}p(a_i)\mid p(a) \][/list]

2006 Pan African, 2

Tags: vieta , algebra , polynomial , rational root theorem , number theory

Let $a, b, c$ be three non-zero integers. It is known that the sums $\frac{a}{b}+\frac{b}{c}+\frac{c}{a}$ and $\frac{b}{a}+\frac{c}{b}+\frac{a}{c}$ are integers. Find these sums.