olymmath

AMO-Bench 2025

AMO-Bench 2025.

Other problems

Problem 1

Divide each side of an equilateral triangle ABCABC into four equal parts. Through each division point, draw lines parallel to the other two sides. The sides of triangleABCABC together with these parallel lines define 1515 lattice points. Find the smallest integer nn such that, no matter which nn points are chosen among these 1515 lattice points, there always exist three points that form an isosceles triangle.

Problem 2

Let pp be a prime number and let aa and bb be non-negative integers. Determine all ordered triples (p,a,b)(p, a, b) for which the expression pa+pbp^a + p^b is a perfect power.

Problem 3

Find all positive integers n\mathbf{n} such that for any: an≥an−1≥an−2≥⋯⋯a2≥a1>0,{a}_{n} \geq {a}_{n - 1} \geq {a}_{n - 2} \geq \cdots \cdots {a}_{2} \geq {a}_{1} > 0, satisfying ∑k=1nak=∑k=1n1ak\mathop{\sum }\limits_{{k = 1}}^{n}{a}_{k} = \mathop{\sum }\limits_{{k = 1}}^{n}\frac{1}{{a}_{k}}, the inequality ∏k=1nakk≥1\mathop{\prod }\limits_{{k = 1}}^{n}{a}_{k}^{k} \geq 1 holds.

Problem 4

Let x1,x2,…,x2025x_1,x_2,\ldots,x_{2025} be real numbers in the interval [0,1][0,1], and let f(x)f(x) be a real-valued function defined on [0,1][0,1]. Find the minimum possible value of max⁡x1,x2,…,x2025∈[0,1]∣∑k=12025f(xk)−(∑k=12025xk)2∣.\max_{x_1,x_2,\ldots,x_{2025}\in[0,1]} \left| \sum_{k=1}^{2025} f(x_k) - \left(\sum_{k=1}^{2025} x_k\right)^2 \right|.

Problem 5

The sequence {an}n=1∞\{a_n\}_{n=1}^{\infty} consists of positive terms, with a1=7a_1=7, a2=2a_2=2, and satisfies the recurrence relation 8an+24=3+4an+1+an(n∈N∗).8a_{n+2}^4=3+4a_{n+1}+a_n (n\in\mathbb{N}^*). Find the general term formula for this sequence.

Problem 6

Let x1,x2,⋯ ,x2024{x}_{1},{x}_{2},\cdots ,{x}_{2024} be positive real numbers such that xk+xm≥km{x}_{k} + {x}_{m} \geq {km} for any 1≤k<m≤20241 \leq k < m \leq {2024}. Find the minimum value of x1+x2+⋯+x2024{x}_{1} + {x}_{2} + \cdots + {x}_{2024}.

Problem 7

⌊n!(n+1)(n+2)⌋\left\lfloor \frac{n!}{(n+1)(n+2)} \right\rfloor represents the greatest integer less than or equal to n!(n+1)(n+2)\frac{n!}{(n+1)(n+2)}. Find all possible values of ⌊n!(n+1)(n+2)⌋−⌊132⋅n!(n+1)(n+2)⌋×32.\left\lfloor \frac{n!}{(n+1)(n+2)} \right\rfloor - \left\lfloor \frac{1}{32} \cdot \frac{n!}{(n+1)(n+2)} \right\rfloor \times 32.

Problem 8

Given that aa is a positive integer and b,cb, c are positive real numbers, find the maximum value of 16(cos⁡a)5−cos⁡(5a)2cos⁡a+cos⁡(3a)⋅a2b+b2ca3+b3+c3.\frac{16(\cos a)^5 - \cos(5a)}{2\cos a + \cos(3a)} \cdot \frac{a^2 b + b^2 c}{a^3 + b^3 + c^3}.

Problem 9

Given that x,y,zx, y, z are all positive real numbers, consider the equation in ww: 11216103270w9−407425607w6+10360232=01121610\sqrt{3270} w^{9} - 407425607 w^{6} + 10360232 = 0 which has kk real roots w1,w2,…,wkw_{1}, w_{2}, \ldots, w_{k}, satisfying w1<w2<⋯<wk.w_{1} < w_{2} < \cdots < w_{k}. If m=(w1+wk)⋅w⌊1+k2⌋,m = (w_{1} + w_{k}) \cdot w_{\left\lfloor \tfrac{1 + k}{2} \right\rfloor}, (where ⌊1+k2⌋\left\lfloor \tfrac{1 + k}{2} \right\rfloor denotes the greatest integer not exceeding 1+k2\tfrac{1 + k}{2}), find the minimum value of x3+y3+z3xyz+63m5(x+y+z)xyz3.\frac{x^{3} + y^{3} + z^{3}}{xyz} + \frac{63m}{5(x+y+z)} \sqrt[3]{xyz}.

Problem 10

Let x,y,zx,y,z be positive real numbers such that xy+xz+yz≠1{xy} + {xz} + {yz} \neq 1, (x2−1)(y2−1)xy+(x2−1)(z2−1)xz+(z2−1)(y2−1)zy=4\frac{\left( {{x}^{2} - 1}\right) \left( {{y}^{2} - 1}\right) }{xy} + \frac{\left( {{x}^{2} - 1}\right) \left( {{z}^{2} - 1}\right) }{xz} + \frac{\left( {{z}^{2} - 1}\right) \left( {{y}^{2} - 1}\right) }{zy} = 4. Find the minimum value of 9x2+13689y2z2−27378yz+28561(y+z)29{x}^{2} + {13689}{y}^{2}{z}^{2} - {27378yz} + \frac{28561}{{\left( y + z\right) }^{2}}.

Problem 11

Let x1,x2,…,xnx_{1}, x_{2}, \ldots, x_{n} be positive numbers satisfying x1+x2+⋯+xn=n.x_{1} + x_{2} + \cdots + x_{n} = n. Find the largest positive integer nn such that 1x12+1x22+⋯+1xn2  ≥x12+x22+⋯+xn2.\frac{1}{x_{1}^{2}} + \frac{1}{x_{2}^{2}} + \cdots + \frac{1}{x_{n}^{2}} \;\geq x_{1}^{2} + x_{2}^{2} + \cdots + x_{n}^{2}.

Problem 12

Space vectors An→(xn,yn,zn)(1≤n≤2052)\overrightarrow{A_n}(x_{n}, y_{n}, z_{n}) (1 \leq n \leq 2052) satisfy that 1+xn,1+yn,1+zn(1≤n≤2052)\sqrt{1+x_{n}}, \sqrt{1+y_{n}}, \sqrt{1+z_{n}} (1 \leq n \leq 2052) are all real numbers, and ∑n=12052xn3=∑n=12052zn3=∑n=12052yn−2052=0,\sum_{n=1}^{2052} x_{n}^{3} = \sum_{n=1}^{2052} z_{n}^{3} = \sum_{n=1}^{2052} y_{n} - 2052 = 0, ∑n=120524zn=∑n=12052xn2=2736,∑n=12052yn2=4210703,∑n=12052yn3=8640361530.\sum_{n=1}^{2052} 4z_{n} = \sum_{n=1}^{2052} x_{n}^{2} = 2736, \sum_{n=1}^{2052} y_{n}^{2} = 4210703, \sum_{n=1}^{2052} y_{n}^{3} = 8640361530.

Find the maximum value of ∣A→1234∣∣A→432∣.\frac{\lvert \overrightarrow{A}_{1234}\rvert}{\lvert \overrightarrow{A}_{432}\rvert}.

Problem 13

Let {ak}\{a_k\} be a sequence of non-negative integers, and {bk}\{b_k\} be a sequence of positive real numbers. Given that: 1.(∑n=12023anbn)(∑k=06731(k+675)(1348−k))=∑k=16741k(2k−1)\left(\sum_{n=1}^{2023} a_n b_n\right)\left( \sum_{k=0}^{673} \frac{1}{(k+675)(1348-k)} \right)= \sum_{k=1}^{674}\frac{1}{k(2k-1)} 2.∑k=113641761k(2k−1)∑k=013641751(k+1364177)(2728352−k)=1+∑n=12023an2bn2\frac{\sum_{k=1}^{1364176}\frac{1}{k(2k-1)}}{\sum_{k=0}^{1364175} \frac{1}{(k+1364177)(2728352-k)}} = 1+\sum_{n=1}^{2023} a_n^2 b_n^2 3.(∑k=055194554201(k+5519455422)(11038910842−k))[(∑n=120232an3bn3)−1]=∑k=155194554211k(2k−1)\left( \sum_{k=0}^{5519455420} \frac{1}{(k+5519455422)(11038910842-k)} \right)\left[\left(\sum^{2023}_{n=1}2a^3_nb^3_n \right)-1\right] =\sum_{k=1}^{5519455421} \frac{1}{k(2k-1)} Find the minimum value of ∑n=12023an4bn4\sum_{n=1}^{2023} a_n^4 b_n^4

Problem 14

Let {an}\{a_n\} be a sequence of positive integers, and let [x][x] denote the greatest integer less than or equal to xx. Consider the system of equations in x,yx,y: ([y]⋅x2+2n+2)(∑k=0n−11(k+n+1)(2n−k))=∑k=1n1k(2k−1),\big([y] \cdot x^2 + 2n + 2\big)\left(\sum_{k=0}^{n-1} \frac{1}{(k+n+1)(2n-k)}\right) = \sum_{k=1}^{n} \frac{1}{k(2k-1)}, 4([x]y2)5+3n(4−n)([x]y2)3−n2(6+n)([x]y2)2+2n2(4−3n)([x]y2)=8n3.4\big([x]y^2\big)^5 + 3n(4-n)\big([x]y^2\big)^3 - n^2(6+n)\big([x]y^2\big)^2 + 2n^2(4-3n)\big([x]y^2\big) = 8n^3.

Suppose there are ana_n distinct real solutions (x,y)(x,y) to this system. Determine whether there exist three positive prime numbers p,k,qp,k,q with p>k>qp > k > q such that ap<ak<aq.a_p < a_k < a_q. If no such primes exist, explain why; if they do exist, find the minimum value of p+k+qp+k+q.

Problem 15

Let a,b,c,da, b, c, d be real numbers such that 4a4+c416+b4+b3d2+27+d24+a2c2=3c2+24a2+8b2+4d2.4a^4 + \frac{c^4}{16} + b^4 + b^3d^2 + 27 + \frac{d^2}{4} + a^2c^2 = 3c^2 + 24a^2 + 8b^2 + 4d^2. Find the minimum value of 4a4+c416+a2c2+12a2+32c2+b4+d44+10+b2d2+2b2+d22a2b2+a2d2+2a2+b2c24+c2d28+c24+3b2+3+32d2.\frac{4a^4 + \frac{c^4}{16} + a^2c^2 + 12a^2 + \frac{3}{2}c^2 + b^4 + \frac{d^4}{4} + 10 + b^2d^2 + 2b^2 + d^2 }{\sqrt{2a^2b^2 + a^2d^2 + 2a^2 + \frac{b^2c^2}{4} + \frac{c^2d^2}{8} + \frac{c^2}{4} + 3b^2 + 3 + \frac{3}{2}d^2}}.

Problem 16

Let nn be a positive integer such that 2≤n≤52 \leq n \leq 5. For each such nn, let AnBnCnDnA_nB_nC_nD_n be a rectangle with vertex AnA_n at (−n,1+62−2n)(-n, 1 + 6 \sqrt{2} - \sqrt{2}n), and vertex BnB_n the reflection of AnA_n through the origin. The line segments AnCnA_nC_n and BnDnB_nD_n are parallel to the xx-axis, and the line segments AnDnA_nD_n and BnCnB_nC_n are parallel to the yy-axis. Let Pi(1≤i≤36)P_i (1 \leq i \leq 36) be 36 distinct points on the curve (y−∣x∣)2+x2=1(y - |x|)^2 + x^2 = 1. For each point PiP_i, let the distances to the 16 sides of the four rectangles be denoted by ri1,ri2,…,ri16r_{i_1}, r_{i_2}, \ldots, r_{i_{16}}. Let di=min⁡(rik),(1≤k≤16)d_i = \min \Big( r_{i_k} \Big) , (1 \leq k \leq 16), and suppose that these values satisfy the condition 3∑i=136di3−15∑i=136di2=−12003 \sum_{i=1}^{36}d_{i}^{3} -15\sum_{i=1}^{36} d_{i}^{2} = -1200. Find the maximum value of ∑i=136di\sum_{i=1}^{36} d_i.

Problem 17

Let {x1,x2,…,x2025}={1,2,…,2025}\{x_1, x_2, \ldots, x_{2025}\} = \{1, 2, \ldots, 2025\}. Find the greatest positive integer less than ∑i=12024xixi+1.\sum_{i=1}^{2024} \frac{x_i}{x_{i+1}}.

Problem 18

Let complex numbers z1,z2,…,z2025z_1, z_2, \ldots, z_{2025} satisfy ∑k=12025zk=0,∑k=12025∣zk∣2=1.\sum_{k=1}^{2025} z_k = 0, \sum_{k=1}^{2025} |z_k|^2 = 1. Find the minimum possible value of max⁡1≤i<j≤2025∣zi−zj∣.\max_{1 \le i < j \le 2025} |z_i - z_j|.

Problem 19

Let a1<a2<⋯<a38a_1 < a_2 < \cdots < a_{38} be positive integers with a1+a2+⋯+a38=1997.a_1 + a_2 + \cdots + a_{38} = 1997. Define bk=min⁡ ⁣(∑i=1kai,∑i=k+138ai),b_k = \min\!\left(\sum_{i=1}^{k} a_i, \sum_{i=k+1}^{38} a_i\right), and let S=max⁡(b1,b2,…,b38),S = \max(b_1, b_2, \ldots, b_{38}), where b38=0b_{38} = 0. Find the minimum possible value of SS.

Problem 20

A school has newly formed 33 classes. It is known that for any two students belonging to different classes, in the third class there are exactly 1010 students who know both of them and 1010 students who know neither of them. Find the total number of students across the three classes.

Problem 21

Given that x,y,zx, y, z are integers satisfying the system {x2−7y4=z,7z4+∑k=1z1k(2k−1)∑k=0z−11(k+z+1)(2z−k)=∑i=01745455621i(2i−1)∑i=01745455611(i+174545563)(349091124−i)\begin{cases} x^2 - 7y^4 = z,\\[6pt] 7z^4+ \frac{\sum_{k=1}^{z} \frac{1}{k(2k-1)}}{\sum_{k=0}^{ z-1} \frac{1}{(k+z+1)(2z-k)}} = \frac{\sum_{i=0}^{174545562} \frac{1}{i(2i-1)}}{\sum_{i=0}^{174545561} \frac{1}{(i+174545563)(349091124-i)}} \end{cases} find the maximum value of x+y+zx+y+z.

Problem 22

Let variables x,y,cx, y, c satisfy x+y+c>13x+y+c > \sqrt{13} with x,y≥0x, y \ge 0. Find the minimum value of (2+x2) (4+y2) (49+6c2+4c3+3c2)(73c+141+c2) (x+y).\frac{(2+x^2)\,(4+y^2)\,\big(49+6c^2+4c\sqrt{3+3c^2}\big)} {\big(7\sqrt{3} c+14\sqrt{1+c^2}\big)\,(x+y)}.

Problem 23

It is known that the equation in u,vu, v, u2−3v4=1u^2 - 3v^4 = 1, has at most four positive integer solutions; and the equation in λ,ι\lambda, \iota, 4λ2−3ι2=14\lambda^2 - 3\iota^2 = 1, has at most four positive integer solutions. If a prime pp satisfies p≡5(mod8)p \equiv 5 \pmod{8}, and integers x,yx, y satisfy (1+x22+9x4+4x63+9+18x2 6)1/3+(1+x22−9x4+4x63+9+18x2 6)1/3=2py2−x3,\left(\frac{1+x^2}{2} + \frac{\sqrt{ 9x^4 + \frac{4x^6}{3} + 9 + 18x^2\,}}{6}\right)^{ 1/3} + \left(\frac{1+x^2}{2} - \frac{\sqrt{ 9x^4 + \frac{4x^6}{3} + 9 + 18x^2\,}}{6}\right)^{ 1/3} = 2py^2 - x^3, find the maximum value of x+yx+y.

Problem 24

Let nn be an integer with n>2n>2. Real numbers a1,a2,…,ana_1, a_2, \ldots, a_n satisfy ∑k=1nak=2n,∑k=1nk ∣ak∣=4n.\sum_{k=1}^{n} a_k = 2n, \sum_{k=1}^{n} k\,|a_k| = 4n. Find the minimum value of a12+a22+⋯+an2a_1^2 + a_2^2 + \cdots + a_n^2.

Problem 25

Given a positive integer kk, find all positive integers nn that can be expressed in the form ab+a+kb+k,\frac{a}{b}+\frac{a+k}{b+k}, where a,b∈N+a, b \in \mathbb{N}^{+}.

Problem 26

Find the number of positive integer solutions (x,y,z)(x, y, z) to the equation x999+y1000=z1001.x^{999} + y^{1000} = z^{1001}.

Problem 27

Find the number of integer solutions to x2+y2+z2+3(xy+yz+zx)+5(x+y+z)+1=0.x^2 + y^2 + z^2 + 3(xy + yz + zx) + 5(x + y + z) + 1 = 0.

Problem 28

For each positive integer k≥2k \ge 2, define f(k)f(k) to be the product of the distinct prime factors of kk. All the coefficients of the polynomial function 9P(x)9P(x) are rational numbers. Suppose 45≤P(2025)≤8145 \le P(2025) \le 81, and there are infinitely many positive integers nn for which P(n)=f(n)P(n) = f(n). How many polynomials P(x)P(x) satisfy these conditions?

Problem 29

Let aa be a prime greater than 100100 with a≡3(mod5)a \equiv 3 \pmod{5}. For complex numbers znz_n (1≤n≤a)(1 \le n \le a), both the real and imaginary parts are nonzero. For each nn, let dnd_n be the distance from the point (n,∣zn∣)(n,\lvert z_n\rvert) to the line y=2025x+2025.y=\frac{202}{5}x+2025. Choose one complex number at random from {zn}n=1a\{z_n\}_{n=1}^a; let pp be the probability that its modulus is a positive integer. Given (2a−∑i=1aidi)2+(3+∑k=2a(2k+2)−∑i=1ai2di)2+(72+∑j=2a ⁣(3j3+3j+12)−∑i=12022i3di)2=0,\bigg(2a-\sum_{i=1}^{a} i^{d_i}\bigg)^{ 2} +\bigg(3+\sum_{k=2}^{a}(2k+2)-\sum_{i=1}^{a} i^{2d_i}\bigg)^{ 2} +\bigg(\frac{7}{2}+\sum_{j=2}^{a}\!\big(3j^3+3j+\tfrac{1}{2}\big)-\sum_{i=1}^{2022} i^{3d_i}\bigg)^{ 2}=0, find the maximum value of pp.

Problem 30

Let p,qp, q be positive integers satisfying the system of congruences: {p≡3(mod911),q≡2(mod997),p≡738(modq);\begin{cases} p \equiv 3 \pmod{911}, \\ q \equiv 2 \pmod{997}, \\ p \equiv 738 \pmod{q}; \end{cases} Let {an},{bn},{cn}\{ a_n \}, \{ b_n \}, \{ c_n \} be periodic sequences of rational numbers satisfying the equations: [4bn+1−3sin⁡(πan)]2+[4cn−1+3sin⁡(πan)]2=0(∀n∈N)\left[ 4b_n + 1 - 3\sin(\pi a_n) \right]^2 + \left[ 4c_n - 1 + 3\sin(\pi a_n) \right]^2 = 0 (\forall n \in \mathbb{N}) and ∣∑i=1pbi3∣+∣∑i=1qci3∣+∣p−3∑i=1pbi∣+∣q−3∑i=1qci2∣=0.\left| \sum_{i=1}^{p} b_i^3 \right|+\left| \sum_{i=1}^{q} c_i^3 \right|+\left| p - 3 \sum_{i=1}^{p} b_i \right|+\left| q - 3 \sum_{i=1}^{q} c_i^2 \right| = 0. Find the minimum value of p+q+2ap2+bq2+cp+q2+(ap+aq−1)2+(bp+cq)2p + q + 2a_p^2 + b_q^2 + c_{p+q}^2 + (a_p + a_{q-1})^2 + (b_p + c_q)^2.

Problem 31

Let (ai,bi)(a_i, b_i), for 1≤i≤20251 \leq i \leq 2025, be 2025 distinct points on the curve 3x2+3y2=8+4xy+2(x+y)∣x−y∣3x^2 + 3y^2 = 8 + 4xy + 2(x + y)|x - y| Let did_i be the distance from the point (ai,bi)(a_i, b_i) to the line x+y=6x + y = 6, and let ⌊di⌋\left\lfloor d_i \right\rfloor denote the greatest integer not exceeding did_i.

It is given that: ri=⌊21−1522(di3−3di2−6di2⋅2+18di+6di⋅2+283+1623)⌋r_i = \left\lfloor \frac{21 - 15\sqrt{2}}{2} \left( d_i^3 - 3d_i^2 - 6d_i^2 \cdot \sqrt{2} + 18d_i + 6d_i \cdot \sqrt{2} + \frac{28}{3} + \frac{16\sqrt{2}}{3} \right) \right\rfloor and that: ∑i=12025ri2=2043,∑i=12025ri=2021\sum_{i=1}^{2025} r_i^2 = 2043, \sum_{i=1}^{2025} r_i = 2021 Find the maximum value of ∑i=12025ri4\sum_{i=1}^{2025} r_i^4

Problem 32

Let xx and yy be positive rational numbers that satisfy: 1+1−2y=y+4x−2+21−2x3−5x−1−2x+1+x22+16⋅9x4+4x63+9+18x23+1+x22−16⋅9x4+4x63+9+18x231 + \sqrt{1 - 2y} = y + \frac{4x - 2 + 2\sqrt{1 - 2x}}{3 - 5x - \sqrt{1 - 2x}} + \sqrt[3]{\frac{1 + x^2}{2} + \frac{1}{6} \cdot \sqrt{9x^4 + \frac{4x^6}{3} + 9 + 18x^2}}+ \sqrt[3]{\frac{1 + x^2}{2} - \frac{1}{6} \cdot \sqrt{9x^4 + \frac{4x^6}{3} + 9 + 18x^2}} Given that kxkx and kyky are both positive integers, find the minimum value of the positive integer kk.

Problem 33

An album contains 25 photos, each showing three people, subject to the following conditions: (1) In each photo, the person on the left is a full brother of the person in the middle, and the person on the right is the daughter of the person in the middle. (2) The person in the middle is different in each of the 25 photos. (3) No two people who appear in the album have a child in common. What is the minimum number of distinct people that must appear in this album?

Problem 34

Find Cmax⁡C_{\max} such that ∀x,y,z∈R\forall x, y, z \in \mathbb{R},f=1+∣x+y+z∣+∣xy+yz+zx∣+∣xyz∣≥C(∣x∣+∣y∣+∣z∣)f = 1 + |x+y+z| + |xy+yz+zx| + |xyz| \geq C(|x| + |y| + |z|)

Problem 35

In a game, a positive integer nn not exceeding 10000 is initially written on a blackboard. Two players, Player 1 and Player 2, take turns making moves, with Player 1 going first. A move consists of erasing a positive integer kk greater than 1 from the blackboard and replacing it with five non-negative integers that sum to kk and whose pairwise differences are at most 1. For example, the integer 11 could be replaced with 2, 2, 2, 2, 3. We also stipulate that 1 couldn't be replaced with five integers. The game ends when a player cannot make a valid move, at which point the other player wins. Assuming both players use an optimal strategy and Player 1 wins, how many possible values of nn are there?

Problem 36

On a 19*19 board, a black or a white stone is placed on each of the 361 squares. An operation consists of choosing one row and one column and reversing the color of all 37 stones in that row and column. Find the largest integer n such that, regardless of the initial arrangement of stones, it is always possible to perform a sequence of such operations so that the number of black stones on the board is at least n.

Problem 37

In △ABC\triangle ABC with AB<AC<BCAB < AC < BC, let OO and II be its circumcenter and incenter, respectively. Let MbM_b and McM_c be the midpoints of the arc ACAC (not containing BB) and the arc ABAB (not containing CC), respectively, on the circumcircle ⊙O\odot O. Let SbS_b be a point on ⊙O\odot O such that ISb⊥BSbIS_b \perp BS_b, and let ScS_c be a point on ⊙O\odot O such that ISc⊥CScIS_c \perp CS_c. Let HaH_a be the intersection of lines MbScM_bS_c and McSbM_cS_b. Points HbH_b and HcH_c are defined analogously.It is given that the lines AHa,BHb,CHcAH_a, BH_b, CH_c are pairwise non-parallel. Let GG be the centroid of the triangle formed by these lines (if the three lines are concurrent, GG is defined as their point of concurrency). Let the side lengths of △ABC\triangle ABC be BC=aBC = a, CA=bCA = b, and AB=cAB = c. Find the product of the distances from point GG to the lines IHa,IHb,IHcIH_a, IH_b, IH_c. (Expressed in terms of a,b,ca, b, c and simplified completely.)

Problem 38

In a dd-dimensional Euclidean space, there are two definitions:

  1. Encapsulation: For a point pp, if there exists a ball centered at pp with sufficiently small radius such that every point within this ball (except pp itself) belongs to at least one convex set KiK_i (where i=1,…,ni=1, \dots, n), then we say point pp is encapsulated by these convex sets;
  2. Contact: For a set KK and a point pp, if pp does not lie inside KK but any neighborhood of pp (no matter how small) contains points from KK, we say point pp contacts set KK (This is equivalent to saying pp is a boundary point of KK). Let K1,K2,K3K_1, K_2, K_3 be three convex sets in dd-dimensional space. Let SS be the set of points encapsulated by these three convex sets. The maximum possible value of ∣S∣|S| is a function theat depends only on the dimension dd. Based on the above definitions and known conditions, the maximum value can be derived. Let f(d,3)=max⁡∣S∣f(d, 3) = \max |S|. Please provide the expression for f(d,3)f(d, 3): f(d,3)=f(d, 3) =

Problem 40

Given positive integers nn and tt with 1≤t<n1 \leq t < n. There are nn cups, all initially upright. An operation consists of choosing tt cups and turning them over. If it is possible to turn all nn cups upside down in mm operations, find the minimum value of mm. (expressed in terms of nn and tt)

Problem 41

Let mm be an odd integer with m≥3m \geq 3. Construct a positive integer xx such that for some positive integers aa and bb, the sequence of consecutive integers a+1,a+2,…,a+ba+1, a+2, \ldots, a+b contains exactly 20232024 terms yy satisfying y≡−1(modm)y \equiv -1 \pmod{m} and y2≡1(modx)y^2 \equiv 1 \pmod{x}, and exactly 2023 terms zz satisfying z≡1(modm)z \equiv 1 \pmod{m} and z2≡1(modx)z^2 \equiv 1 \pmod{x}.

Problem 42

A point M on an infinite number line moves one unit to the left or to the right at each step. The probability of moving to the right is p(p>12)p (p > \frac{1}{2}), and the probability of moving to the left is 1−p1-p. The point M starts at the origin x=0x = 0. Let xx be the probability that M is at position x=3x = 3 after nn moves, where n≥2n \geq 2, and let yy be the probability that M is at position x=4x = 4 after mm moves, where m≥2m \geq 2. Find the conditions on mm and nn such that x>(1−p)yx > (1-p)y.

Problem 43

Let f(x),g(x),h(x)f(x),g(x),h(x) be functions defined on the set of positive integers. Let ⌊x2⌋\left\lfloor \tfrac{x}{2}\right\rfloor denote the greatest integer less than or equal to x2\tfrac{x}{2}. Define f(x)f(x) to be the number of integers in the list 1,2,3,…,⌊x2⌋1,2,3,\dots,\left\lfloor \tfrac{x}{2}\right\rfloor that are coprime to xx. If p1,p2,…,pkp_{1},p_{2},\dots,p_{k} are distinct primes and y=p1α1p2α2⋯pkαky=p_{1}^{\alpha_{1}}p_{2}^{\alpha_{2}}\cdots p_{k}^{\alpha_{k}}, then g(y)=max⁡{p1α1,p2α2, …,pkαk }.g(y)=\max\{ p_{1}^{\alpha_{1}}, p_{2}^{\alpha_{2}},\,\dots, p_{k}^{\alpha_{k}}\,\}. For a positive integer zz, let h(z)h(z) be the least positive integer mm such that z∣m!z\mid m!. Find all integers b>1b>1 such that f(b)=h ⁣(g(b2)).f(b)=h\!\big(g(b^{2})\big).

Problem 44

Let a=log⁡3(12∑n=0676(−1)n(20283n))a=\log_3\bigg(\frac{1}{2}\sum\limits_{n=0}^{676}(-1)^n{2028 \choose 3n}\bigg). Calculate the sum of distinct prime factors of a2+(a−1)4a^2+(a-1)^4.

Problem 45

Find the largest positive integer nn that satisfies the following property: there exists a sequence of nn positive integers a1,⋯ ,an{a}_{1},\cdots ,{a}_{n} such that ai≤22025(∀1≤i≤n){a}_{i} \leq {2}^{2025}\left( {\forall 1 \leq i \leq n}\right), and for any 1≤i<j≤n1 \leq i < j \leq n, there is no non-empty proper subset A⊂{i,i+1,⋯ ,j}A \subset \{ i,i + 1,\cdots ,j\} such that ∑k∈Aak=∑k∈{i,i+1,⋯ ,j}−Aak.(1)\mathop{\sum }\limits_{{k \in A}}{a}_{k} = \mathop{\sum }\limits_{{k \in \{ i,i + 1,\cdots ,j\} - A}}{a}_{k}. \tag{1}

Problem 46

There are n×n×nn\times n\times n mud blocks on the ground. A miner starts digging through one of the blocks. Each time, he can only dig a face-adjacent block until all blocks are dug out. If he digs the blocks consecutively and for nn times these blocks are all in a line, then the miner is described as to have dug a straight line'' once. Find the maximum possible number the miner can dig a straight line''.

Problem 47

Assume that graph GG has 5050 vertices, and for any two non-adjacent vertices, they have exactly two common neighbors. Vertices v1v_1 and v2v_2 are adjacent and have no common neighbors, the degree of v1v_1 is d(v1)=11d(v_1)=11. The parameter MM is defined as: if such a graph GG exists, then M=max(d(v2)−d(v1))M=max(d(v_2)-d(v_1)); otherwise, M=0M=0. Let aa be the smallest positive real root of the equation x6−4x5+7x4−25x3+38x2−6x+34=M(2x3−4x2+3x−19−M)x^{6}-4x^{5}+7x^{4}-25x^{3}+38x^{2}-6x+34=M(2x^3-4x^2+3x-19-M), find the remainder of the closest integer to a25a^{25} divided by 10001000.

Problem 48

A city is going to be built as a 10×1010\times 10 square grid of blocks. Now, the city is planning to set up security booths in some blocks. To ensure the safety of the entire city, city safety regulations require that for any block (regardless of whether it has a security booth itself), at least one of its four adjacent blocks (up, down, left, right) must have a security booth. How many security booths are needed at a minimum to satisfy the safety regulations?

Problem 49

In the Cartesian plane, there is a lamp at every integer lattice point, each with two states: on'' and off''. The lamp board features a special switching system: pressing any lamp toggles the states of all lamps in its entire row and entire column (on to off, and off to on). Define f(x)=x2−18x+23f(x)=x^2-18x+23 and g(x)=37x+18g(x)=37x+18. The equation f(f(x))=g(x)f(f(x))=g(x) has real roots a1,a2,a3,a4a_1,a_2,a_3,a_4 with a1<a2<a3<a4a_1 < a_2 < a_3 < a_4. You can operate the switches at coordinates (x,y)(x,y) where 1≤x≤171\leq x\leq 17 and 1≤y≤a2+a31\leq y\leq a_2+a_3. Regardless of the initial state of the lamp board, what is the minimum number of lamps within this operable rectangular region that you can guarantee will be lit after performing operations using this system?

Problem 50

Let the polynomial f(x)=x6−11x5+28x4+2x3+57x2+13x+30f(x)=x^6 - 11x^5 + 28x^4 + 2x^3 + 57x^2 + 13x + 30, and let α\alpha be the smallest positive real root of the equation f(x)=0f(x)=0. Set NN as the remainder of the closest integer to α35\alpha^{35} divided by 1498. A logistics company warehouses pallets with serial numbers m=1,2,…,Mm=1,2,\dots, M. To simplify the sampling-judgment'' process, three quality inspectors use their respective cyclic-power residue'' rules: Inspector A uses a cycle of 77 pallets'' rule to record the remainder of serial number mm divided by 77. If this remainder is a non-zero quadratic residue of modulo 77 (there exists an rr coprime to 77 such that r2≡m(mod7)r^2\equiv m\pmod7), it is marked as passed''; Inspector B uses a cycle of 1111 pallets'' rule to record the remainder of serial number mm divided by 1111. If this remainder is a non-zero cubic residue of modulo 1111 (there exists an rr coprime to 1111 such that r3≡m(mod11)r^3\equiv m\pmod{11}), it is marked as passed''; Inspector C uses a cycle of 1313 pallets'' rule to record the remainder of serial number mm divided by 1313. If this remainder is a non-zero quartic residue of modulo 1313 (there exists an rr coprime to 1313 such that r4≡m(mod13)r^4\equiv m\pmod{13}), it is marked as passed''. A serial number mm is marked as qualified'' if and only if all three inspectors mark it as passed''. Let the total number of qualified serial numbers be counted within the range 1≤m≤M1 \le m \le M, where the integer MM satisfies M−724=NM-724=N. How many ``qualified'' serial numbers are there in total?