# Solutions of q=xy+yz+zxq=\frac{x}{y} +\frac{y}{z} + \frac{z}{x} s.t. q≥3q \geq 3

Is it true that for every rational $q \geq 3$ , the following equation has a solution over $\mathbb N$ ?

The problem

$N=\frac{x}{y}+\frac{y}{z}+\frac{z}{x}$

with $N,x,y,z \in \mathbb{Z}$ was considered by Andrew Bremner and Richard Guy in “Two more representation problems” published in the Proceedings of the Edinburgh Mathematical Society, vol. 40 pp.1-17 in 1997. An online copy is available here. They showed solutions only occurred for those $N$ where the elliptic curve

$t^2=u^3+N^2u^2+8Nu+16$

has rank at least $1$.

For small $N>0$, the first solution is for $N=6$, with $x=18$, $y=4$ and $z=3$.