Some MATH
by math154, Jul 19, 2010, 5:01 PM
... since there has been a notable lack of it.
So these are just some random MOP problems that I liked. Someone tell me if the tests and team contests are copyrighted or something.
Hidden for length
Darn the lack of combo is disturbing, but I suck too much. There's not much geometry since good geometry problems are not that hard to find... In other news, Google Chrome seems to be very good at dealing with rickrolls.
So these are just some random MOP problems that I liked. Someone tell me if the tests and team contests are copyrighted or something.
Hidden for length
1. The positive integer
has a prime divisor greater than
. Find the smallest positive integer
such that there exists a finite set
of distinct positive integers satisfying (i)
and
are the least and greatest elements, respectively, in
, and (ii) the product of all the numbers in
is a perfect square.
2. Let
be positive integers and
Find all integer values that
can take.
3. Show that there exists a sequence
of positive integers such that
(i) the sequence
contains each positive integer exactly once
(ii) the sequence
also contains each positive integer exactly once.
4 (MOP 2002). Show that there are infinitely many ordered quadruples of integers
such that all six of
are perfect squares.
5 (MOP 2004). Find all functions
such that
![\[f(xf(y)) = (1-y)f(xy)+x^2y^2f(y).\]](//latex.artofproblemsolving.com/1/1/f/11faeb310b5be4255a9e229f6c1811a70a01a24f.png)
6 (TST 2000.4). Let
be a positive integer. Prove that
![\[\binom{n}{0}^{-1}+\binom{n}{1}^{-1}+\cdots+\binom{n}{n}^{-1}=\frac{n+1}{2^{n+1}}\left(\frac{2}{1}+\frac{2^{2}}{2}+\cdots+\frac{2^{n+1}}{n+1}\right).\]](//latex.artofproblemsolving.com/f/a/8/fa8b2f5da90619659078640498cbe457d72999b3.png)
7 (2010 Green 4.3). Fix
points in space in such a way that no four of them are in the same plane, and choose any
segments determined by the given points. Determine the least number of points that are the vertices of a triangle formed by the chosen segments.
8 (Red and Green Team Contest 2.2). Let
be a point exterior to circle
and let
be points on
so that
are the tangents from
to
. Let
be a point on minor arc
such that
and let
be the center of
. Let
and
intersect at
, and
and
intersect at
. Prove that the circumcenters of
are collinear.
9 (Red and Green Team Contest 4.3b). Let
be a positive integer greater than
. Prove there exists a positive integer
with the property that for every integer
greater than
the open interval
contains
distinct integers whose product is an
power of an integer. (Part (a) was this. I don't know how to do part (b) yet.)
Edit: see corrected version here.
10 (Red and Green Team Contest 4.6; 2006 Bulgarian MO). Let
denote the set of positive real numbers. Suppose
is a function such that
for all
. Prove that
for all positive real numbers
, and find all possible functions
.
11 (Red and Green Team Contest 4.7; 2006 Bulgarian MO). Let
be a prime such that
divides
. Prove that for any positive integer
, the number
has at least three distinct prime divisors.
12 (Black Team Contest 1.5). Find all positive integer solutions to
![\[(a+b)^x=a^y+b^y.\]](//latex.artofproblemsolving.com/8/a/2/8a23adeaea37adfe9c196a243b568cdc4e86ef6e.png)
13 (Black Team Contest 1.7). Let
be positive integers satisfying
. Find, with proof, the smallest number of total prime factors of
. (So
adds
to the count.)








2. Let

![\[P = \frac{x^3-y}{1+xy}.\]](http://latex.artofproblemsolving.com/0/e/1/0e1741844cd0a1fd05df5106dae9b31b9b7d68e9.png)

3. Show that there exists a sequence

(i) the sequence

(ii) the sequence

4 (MOP 2002). Show that there are infinitely many ordered quadruples of integers

![\[xy+1,xz+1,xw+1,yz+1,yw+1,zw+1\]](http://latex.artofproblemsolving.com/4/e/3/4e3151470bfb1aec29ec74abd1ebb7e49a5ebb80.png)
5 (MOP 2004). Find all functions

![\[f(xf(y)) = (1-y)f(xy)+x^2y^2f(y).\]](http://latex.artofproblemsolving.com/1/1/f/11faeb310b5be4255a9e229f6c1811a70a01a24f.png)
6 (TST 2000.4). Let

![\[\binom{n}{0}^{-1}+\binom{n}{1}^{-1}+\cdots+\binom{n}{n}^{-1}=\frac{n+1}{2^{n+1}}\left(\frac{2}{1}+\frac{2^{2}}{2}+\cdots+\frac{2^{n+1}}{n+1}\right).\]](http://latex.artofproblemsolving.com/f/a/8/fa8b2f5da90619659078640498cbe457d72999b3.png)
7 (2010 Green 4.3). Fix


8 (Red and Green Team Contest 2.2). Let



















9 (Red and Green Team Contest 4.3b). Let








Edit: see corrected version here.
10 (Red and Green Team Contest 4.6; 2006 Bulgarian MO). Let


![\[f(x+y)-f(x-y)=4\sqrt{f(x)f(y)}\]](http://latex.artofproblemsolving.com/8/c/f/8cf672f8fc2e4addb4c28c03ccde42475fbb8068.png)




11 (Red and Green Team Contest 4.7; 2006 Bulgarian MO). Let





12 (Black Team Contest 1.5). Find all positive integer solutions to
![\[(a+b)^x=a^y+b^y.\]](http://latex.artofproblemsolving.com/8/a/2/8a23adeaea37adfe9c196a243b568cdc4e86ef6e.png)
13 (Black Team Contest 1.7). Let





Darn the lack of combo is disturbing, but I suck too much. There's not much geometry since good geometry problems are not that hard to find... In other news, Google Chrome seems to be very good at dealing with rickrolls.
This post has been edited 11 times. Last edited by math154, Dec 27, 2012, 1:05 AM