[/quote]
,
be reals such that 
and 
.
and a set 
disting positive integers smaller than 
are given. Prove that there exists a positive integer 
that can be written in the form 
,
in at least 
different ways.
be positive real numbers satisfying 
.![\[
3(x^{\frac{2}{3}} + y^{\frac{2}{3}}) \geq 4 + 2x^{\frac{1}{3}}y^{\frac{1}{3}}.
\]](http://latex.artofproblemsolving.com/f/3/c/f3cd114f909f388eacee142d3f90d07f6b149131.png)
be real numbers such that 
.
Let 
.
and 
,
as follows:
where 
are all the positive divisors of 
.
Find all positive integers 
.
Find all positive integers 
.
be a convex quadrilateral. Suppose that the circles with diameters 
and 
intersect at points 
and 
.
,
attaining all positive values and positive numbers 
are given. Numbers 
satisfy
for every 
.
.
?
and 
points on a plane is 
,
points of a plane, no three of which are collinear, consisting of 
,
be the set of all positive integers not exceeding ![\[
P_n(x) = \sum_{k \in S_n} x^{k - 1}
\]](http://latex.artofproblemsolving.com/3/a/c/3ac60cb70baf4dfcf297e9af87480a8ee34ba70c.png)
and a polynomial 
with integer coefficients such that![\[
P_n(x) = (x^{r_n} + 1) Q_n(x).
\]](http://latex.artofproblemsolving.com/7/0/e/70e19a9d3e0a7e97abc7aa08d3f23126c14ea7d0.png)
is irreducible in ![$\mathbb{Z}[x]$](http://latex.artofproblemsolving.com/4/b/7/4b7d768fffbb7a1a6163af392ed348f2d49d8783.png)
.
Y by Amir Hossein, Adventure10, Mango247
Two fixed lines 
and 
are perpendicular to each other at a point 
. Points 
and 
are on and both are on one side of line . We draw the circle 
with center and radius 
. A variable point 
is on line . Line 
cuts circle in 
. Parallel to 
from intersects 
in 
. Find the locus of the point .
Proposed by Nima Hamidi
and 
are perpendicular to each other at a point 
. Points 
and 
are on and both are on one side of line . We draw the circle 
with center and radius 
. A variable point 
is on line . Line 
cuts circle in 
. Parallel to 
from intersects 
in 
. Find the locus of the point .Proposed by Nima Hamidi
This post has been edited 1 time. Last edited by goodar2006, Sep 28, 2012, 1:26 PM
and 
is the midpoint of 
and 
denotes the radius of 
is the orthogonal projection of 
From 
and 
we get
and 
we obtain 
vertex 
