Question 19
Let $m$ and $n$ be positive integers of different parity. Show that
$$
(m + 3n)(5m + 7n)(7m + 5n)(3m + n)
$$
can never be a perfect square.
$$
(m + 3n)(5m + 7n)(7m + 5n)(3m + n)
$$
can never be a perfect square.
MathNet 2008-part-04 — 165 problems (EN–VI) Question 19
Math Olympiad Vault · MathNet 2008-part-04 — 165 problems (EN–VI)