Question 61
Find all positive integers $x,y$ with $x\leq y$ such that
$$
\frac{(x+y)(xy-1)}{xy+1}=p,
$$
where $p$ is a prime number.
$$
\frac{(x+y)(xy-1)}{xy+1}=p,
$$
where $p$ is a prime number.
MathNet 2021 — Part 10 Question 61
Math Olympiad Vault · MathNet 2021 — Part 10