Question 2
Find all quadruples $(a, b, c, d)$ of non-negative integers such that $ab = 2(1 + cd)$ and there exists a non-degenerate triangle with sides of length $a - c$, $b - d$, and $c + d$.
Math Olympiad Vault · MathNet 2022-part-04 — 197 problems (EN–VI)