Determine all integer solutions (x,y,z) for the system of equations
x²z + y²z + 4xy = 40,
x² + y² + xyz = 20
The above posts were certainly enlightening. I had convinced myself that I had found an infinite number of solutions to this problem, but only after looking at what others had posted did I realize my error. So, almost all of my "solutions" had to be discarded, as they actually didn't satisfy the original equations. However, I did end up with 4 possible solution triples. Two of them have been mentioned previously, namely
(1,1,18) and (-1,-1,18).
There is another pair of solutions though! If you are keen to try and find them on your own, then don't read any further, as I will give them away below.
The other pair is (2,2,3) and (-2,-2,3). As far as I could tell in my calculations I exhausted all other possibilities. So I believe that these are the only 4 answers. It will certainly be interesting to see any more correspondence on this problem! Thanks to Bractals for the great puzzle.