AoPS Academy
[/quote]
, do not answer with "
is a solution" only. Either you post any kind of proof or at least something unexpected (like "
is the smallest solution). Someone that does not see that is a solution of the above without your post is completely wrong here, this is an IMO-level forum.
are nonzero real numbers, find the minimum value of the expression![\[
P = \left| \frac{b + c + d}{a} \right| + \left| \frac{c + d + a}{b} \right| + \left| \frac{d + a + b}{c} \right| + \left| \frac{a + b + c}{d} \right|.
\]](http://latex.artofproblemsolving.com/e/3/e/e3e63937c4badb9bcb47e30778f2165e2df5ae46.png)
and integers 
, prove that for any 
positive numbers 
satisfying 
for 
(with the convention 
), the following inequality holds:![\[
\sum_{j=1}^n a_j^{2m-1} \leq \frac{mt}{2} \left( \sum_{j=1}^n a_j^{m-1} \right)^2.
\]](http://latex.artofproblemsolving.com/5/c/d/5cd52e9ce307563bde96f697a75079229d4bfcc2.png)
be non-negative real numbers such that 
and![\[
\frac{25a + 36b + 49c}{5a + 6b + 7c} + \frac{25b + 36c + 49a}{5b + 6c + 7a} + \frac{25c + 36a + 49b}{5c + 6a + 7b} = 18.
\]](http://latex.artofproblemsolving.com/a/8/a/a8a56fe414b713138e1adc48cdcedcc23200843c.png)
Prove that exactly two of the numbers are equal to 0.
is inscribed in circle 
. The interior angle bisector of angle 
intersects side 
and at 
and 
(other than ), respectively. Let 
be the midpoint of side . The circumcircle of triangle 
intersects sides 
and 
again at 
and 
(other than ), respectively. Let 
be the midpoint of segment 
, and let 
be the foot of the perpendicular from to line 
. Prove that line 
is tangent to the circumcircle of triangle 
.
prove that
be an acute angled triangle with 
and incircle 
. Let touch the sides 
and at 
and 
respectively. Let 
and 
be points outside 
satisfying ![\[\angle BDX = \angle XEA = \angle YDC = \angle AFY = 45^{\circ}.\]](http://latex.artofproblemsolving.com/4/7/0/470b0486fa1342c4b6444ec1e3731c23bbb842fb.png)
Prove that the circumcircles of 
and meet at a point 
.
be a fixed integer. The cells of an 
table are filled with the integers from 
to 
with each number appearing exactly once. Let be the number of unordered quadruples of cells on this board which form an axis-aligned rectangle, with the two smaller integers being on opposite vertices of this rectangle. Find the largest possible value of .
of 
touch at , 
, let 
denote the line tangent to through 
. Define 
such that 
. Prove that the circumcenter 
of lies on 
.
Prove that
Let 
Prove that
. Prove that
the equation 
such that 
=
wich belongs to set A ?
.
The RHS becomes 
,
,
Thus, 
.
,
.
and 
.
,
,
.