Twelve Points On Two Orbits

Geometry Level 5

A triangle has vertices A = ( 0 , 0 ) , B = ( 24 , 0 ) , C = ( 6 , 12 ) A=(0,0), B=(24,0), C=(6,12) . The equation of its Steiner inellipse has the form: a y 2 + b x y + c x 2 + d y + e x + f = 0 a{ y }^{ 2 }+bxy+{ cx }^{ 2 }+dy+ex+f=0

where a , b , c , d , e , f a, b, c, d, e, f are co-prime integers with a > 0 a>0 .

The equation of another ellipse that trisects all three sides of triangle A B C ABC has the equation:

a y 2 + b x y + c x 2 + d y + e x + f 2 = 0 a{ y }^{ 2 }+bxy+{ cx }^{ 2 }+dy+ex+f_2=0

where a , b , c , d , e , f 2 a, b, c, d, e, f_2 are co-prime integers, and a > 0 a>0 .

If f f 2 = m n \dfrac{f}{f_2}=\dfrac{m}{n} , where m , n m,n are coprime positive integers, find m + n . m + n.


The problem is original


The answer is 17.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Maria Kozlowska
Feb 3, 2016

Midpoints of triangle sides and midpoints between triangle vertices and the centroid all lie on Steiner ellipse. Ellipses have equations:

4 x ² + 13 y ² + 4 x y 96 x 144 y + 512 = 0 4x² + 13y² + 4x y - 96x - 144y + 512 = 0 4 x ² + 13 y ² + 4 x y 96 x 144 y + 576 = 0 4x² + 13y² + 4x y - 96x - 144y + 576= 0

f f 2 = 8 9 \frac{f}{f_2}=\frac{8}{9}

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...