Alon Amit's answer to How do you find the integer solutions to x/(y+z) + y/(z+x) + z/(x+y) = 4? https://www.quora.com/How-do-you-find-the-integer-solutions-to-frac-x-y+z-+-frac-y-z+x-+-frac-z-x+y-4/answer/Alon-Amit おー、面白い！