By symmetry, let's assume x≥y≥z. Then we have (1+1z)3≥(1+1x)(1+1y)(1+1z)=2 This implies z≤3. Do casework:
- (1) z=1_ This implies (1+1x)(1+1y)=1. This cannot hold because (1+1x)>1 and (1+1y)>1 means (1+1x)(1+1y)>1.
- (2) z=2_ This implies (1+1x)(1+1y)=43. Because x≥y, therefore (1+1y)2≥(1+1x)(1+1y)=43⟹2≤y≤6 Setting y=2,3,4,5, and 6, respectively, finds (x,y,z)=(15,4,2),(9,5,2) are solutions.
- (3) z=3_ This implies (1+1x)(1+1y)=32. By a similar reasoning, we have (1+1y)2≥(1+1x)(1+1y)=32⟹3≤y≤4 Setting y=3 and 4 respectively finding (x,y,z)=(8,3,3) and (5,4,3) are solutions.
Therefore, the solutions are all the permutations of (7,6,2),(9,5,2),(15,4,2),(8,3,3),(5,4,3).