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Project: Playground
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#define the elliptic curve corresponding to the equation a/(b+c)+b/(a+c)+c/(a+b)=4 ee=EllipticCurve([0,109,0,224,0])
ee
Elliptic Curve defined by y^2 = x^3 + 109*x^2 + 224*x over Rational Field
ee.rank()
1
ee.gens()
[(-100 : 260 : 1)]
P=ee(-100,260) # this is a generator for the group of rational points
2*P # just a check
(8836/25 : -950716/125 : 1)
# Convert a point (x,y) on the elliptic curve back to (a,b,c). This has N as an argument, but in our case N=4. # We also ensure that the result is all integers, by multiplying by a suitable lcm. def orig(P,N): x=P[0] y=P[1] a=(8*(N+3)-x+y)/(2*(N+3)*(4-x)) b=(8*(N+3)-x-y)/(2*(N+3)*(4-x)) c=(-4*(N+3)-(N+2)*x)/((N+3)*(4-x)) da=denominator(a) db=denominator(b) dc=denominator(c) l=lcm(da,lcm(db,dc)) return [a*l,b*l,c*l]
orig(P,4)
[4, -1, 11]
u=orig(9*P,4) # Bremner and MacLeod noticed that 9P yields a positive solution.
(a,b,c)=(u[0],u[1],u[2]) (a,b,c)
(154476802108746166441951315019919837485664325669565431700026634898253202035277999, 36875131794129999827197811565225474825492979968971970996283137471637224634055579, 4373612677928697257861252602371390152816537558161613618621437993378423467772036)
a/(b+c)+b/(a+c)+c/(a+b)
4
a%100003
68745