[/quote]
,
with real coefficients such that 
holds for all nonzero real numbers 
satisfying 
.
.![\[ \frac { x^5-x^2 }{x^5+y^2+z^2} + \frac {y^5-y^2}{x^2+y^5+z^2} + \frac {z^5-z^2}{x^2+y^2+z^5} \geq 0 . \]](http://latex.artofproblemsolving.com/a/1/4/a14adf0f1e35df57c734c7df701d5a67da22dc3c.png)
and orthocenter 
.
is 
respectively. A point 
satisfies that 
and 
are both tangent to 
.
and tangent to 
intesects 
is an arbitrary point on 
,
is the second intesection point of 
and 
.
are concyclic.
so that 
can be a perfect square
be an isosceles triangle with 
.
be a point on 
.
be a point inside the triangle such that 
and![\[
CL \cdot BD = BL \cdot CD.
\]](http://latex.artofproblemsolving.com/1/6/7/16771838c95f86e92f79b8d049e46ab473e6287d.png)
Prove that the circumcenter of triangle 
lies on line 
.
such that
for all real numbers 
such that 
.
such that for all 
,![\[f(x+yf(x))+y = xy + f(x+y).\]](http://latex.artofproblemsolving.com/c/f/3/cf3d20a041c27244e90876119b4568b7a3e13c03.png)
be an integer, let 
be a set of 
elements, and let 
,
such that ![\[ A_i \cap A_j \not= \emptyset, A_i \cap A_k \not= \emptyset, A_j \cap A_k \not= \emptyset, \;\textrm{imply}\ \;A_i \cap A_j \cap A_k \not= \emptyset \ .\]](http://latex.artofproblemsolving.com/c/1/1/c113f5cdce00dfec6714c382a8e1bc74f188f025.png)
Show that 
.
such that 
or 
,![\[
1 \leq a_1 < a_2 < \cdots < a_{(p-1)/2} < p
\]](http://latex.artofproblemsolving.com/6/8/e/68e3d73edec43b2cc480832adf23bbbb5f4c7bee.png)
such that![\[
\prod_{\substack{1 \leq i < j \leq (p-1)/2}} (a_i + a_j)^2 \equiv 1 \pmod{p}.
\]](http://latex.artofproblemsolving.com/2/9/e/29edf6ab8cee2a526e7753a140c5a291e987856a.png)
denote the maximum number of 
-
board such that each 
such that![\[
f(N) \leq cN^2
\]](http://latex.artofproblemsolving.com/7/4/8/748109c3d63203f9a67a167434e10a909f38e83f.png)
for all positive integers 
.
Y by aeryde.xin, rdj5933mile5, dft, Amir Hossein, Adventure10, and 4 other users
Hi all!
Contest season is coming up! To help with the preparation, I'm planning to host a mock AMC 12 soon. I would like to make it an online contest, so that you guys can submit answers and we can post scores, and so on. I'm putting the tentative dates as the weekend of Jan 21-22, during which sending in answers is allowed. Of course, problems will be available for practice after that as well.
Sounds good? Keep practicing, and stay posted!
UPDATE: Problems have been posted; please see below. You have until 11:59PM Pacific Time, Sunday 22nd, to PM me the answers.
As usual, 6 points for a correct answer, 1.5 points for not answering, and 0 points for a wrong answer.
Contest season is coming up! To help with the preparation, I'm planning to host a mock AMC 12 soon. I would like to make it an online contest, so that you guys can submit answers and we can post scores, and so on. I'm putting the tentative dates as the weekend of Jan 21-22, during which sending in answers is allowed. Of course, problems will be available for practice after that as well.
Sounds good? Keep practicing, and stay posted!
UPDATE: Problems have been posted; please see below. You have until 11:59PM Pacific Time, Sunday 22nd, to PM me the answers.
As usual, 6 points for a correct answer, 1.5 points for not answering, and 0 points for a wrong answer.
This post has been edited 4 times. Last edited by python123, Jan 19, 2012, 1:45 AM
?
and 
,
.
such that 
?
be a regular pentagon. Segments 
and 
intersect at 
.
?
.
,
?
be a square. Let 
be the midpoint of side 
,
be the intersection of segments 
and 
?
,
are constants. If 
,
?
.
be a point on 
such that 
and 
,
.
?
.
and 
are the roots of the equation 
,
?
.
terms of it?
.
?
be equilateral triangles. 
,
is perpendicular to 
,
be integers such that 
,
for 
.
?
,
be the sum of the digits of 
.
?
is defined by 
,
for 
.
approach?
are there such that 
and 
is divisible by 
?
and 
.
.
.
,
?
is tangent to the circle 
.
,
?
,
.
be real numbers. Suppose that 
and 
.
?
.
.
?
and a point 
on the curve 
is in which of the following range?
.
![\[ \frac{ad+bc}{bd}+\frac{ab+cd}{ac}=\frac{13}{2}\]](http://latex.artofproblemsolving.com/3/4/0/340f67afdfa74d3a4db98cf8a4c6dff97e7fd6e2.png)
![\[ \frac{ad+bc}{cd}+\frac{bc+ad}{ab}=9\]](http://latex.artofproblemsolving.com/4/a/6/4a68194f779595605b60d6d308e310525c4304ea.png)
yields![\[\frac{(ad+bc)(ab+cd)}{bd\cdot ac}=0 \]](http://latex.artofproblemsolving.com/4/a/e/4aea0550b49b53238762b9f3c0e50d2ce7e1e18d.png)
and 
.![\[ x+y=\frac{13}{2}\]](http://latex.artofproblemsolving.com/2/9/8/2984863e0c29cccc29c1b962f5a507b9cdc94608.png)
![\[ xy=9\]](http://latex.artofproblemsolving.com/d/2/d/d2d4be24cb9072334f27f5db2e8dc2d25a0a351f.png)
.
,
.
,
and 
.
.
everywhere, all we need to do is translate 
.
must equal the slope of the line 
.
However, I thought this test was too easy (22 looks like a challenge problem from a school textbook) and contained too many problems from previous years.
)
.
which does what?
.
.
.
take on, because 
ordered pairs, giving us the answer 
.
,
mod 
.
.
