Is the quartic Diophantine equation $A^4+h{B}^4=C^4+h{D}^4$ solvable for any integer $h$?

Farzali Izadi, Mehdi Baghalagdam

The Diophantine equation $A^4+h{B}^4=C^4+h{D}^4$, where $h$ is a fixed arbitrary positive integer, has been investigated by some authors. Currently, by computer search, the integer sol…