MathDB
Indonesia Juniors 2020 day 1 KSN SMP

Source:

November 10, 2021
algebrageometrycombinatoricsnumber theoryindonesia juniors

Problem Statement

p1. Let ABAB be the diameter of the circle and PP is a point outside the circle. The lines PQPQ and PRPR are tangent to the circles at points QQ and RR. The lines PHPH is perpendicular on line ABAB at HH . Line PHPH intersects ARAR at SS. If QPH=40o\angle QPH =40^o and QSA=30o\angle QSA =30^o, find RPS\angle RPS.
p2. There is a meeting consisting of 4040 seats attended by 1616 invited guests. If each invited guest must be limited to at least 1 1 chair, then determine the number of arrangements.
p3. In the crossword puzzle, in the following crossword puzzle, each box can only be filled with numbers from 1 1 to 99. https://cdn.artofproblemsolving.com/attachments/2/e/224b79c25305e8ed9a8a4da51059f961b9fbf8.png Across: 1. Composite factor of 10011001 3. Non-polyndromic numbers 5. p×q3p\times q^3, with pqp\ne q and p,qp,q primes
Down: 1. a1a-1 and b+1b+1 , aba\ne b and p,qp,q primes 2. multiple of 99 4. p3×qp^3 \times q, with pqp\ne q and p,qp,q primes
p4. Given a function f:RRf:R \to R and a function g:RRg:R \to R, so that it fulfills the following figure: https://cdn.artofproblemsolving.com/attachments/b/9/fb8e4e08861a3572412ae958828dce1c1e137a.png Find the number of values ​​of xx, such that (f(x))22g(x)x{10,9,8,,9,10}(f(x))^2-2g(x)-x \in\{-10,-9,-8,…,9,10\}.
p5. In a garden that is rectangular in shape, there is a watchtower in each corner and in the garden there is a monitoring tower. Small areas will be made in the shape of a triangle so that the corner points are towers (free of monitoring and/or supervisory towers). Let k(m,n)k(m,n) be the number of small areas created if there are mm control towers and nn monitoring towers. a. Find the values ​​of k(4,1)k(4,1), k(4,2)k(4,2), k(4,3)k(4,3), and k(4,4)k(4,4) b. Find the general formula k(m,n)k(m,n) with mm and nn natural numbers .