AoPS Academy
be distinct natural numbers each of which has exactly 
positive integer factors. For instance, 
has exactly positive integer factors 
. Assume that no prime larger than 
divides any of the 
's. Show that there must be some perfect cube among the 's.
be an integer. Prove that 
can be written as a polynomial with integer coefficients in the variables 
, 
and 
.
, where 
are real numbers such that 
is an integral multiple of 
. Using (a) or otherwise show that if 
, then 
for all positive integers 
.
be the orthocenter of an acute-angled triangle 
. The circle 
centered at the midpoint of 
and passing through intersects the sideline at points 
and 
. Similarly, define the points 
, 
, 
and 
., , , , and are concyclic.
with real coefficient. It is known that 
and 
. Prove that 
can't have 
distinct real roots.
be a triangle such that 
. Let 
be the foot of the angle bisector from 
. Let 
be the circumscribed circle of triangle and call 
the intersection of the tangent to at 
with line 
. Show that 
.
be a triangle such that . Let be the foot of the angle bisector from . Let be the circumscribed circle of triangle and call the intersection of the tangent to at with line . Show that .
