From the given conditions, we have
xz=2z−y,xy=2x−z,yz=2y−x.
Taking the sum of these equations, side by side, we have
xy+yz+zx=x+y+z=T.
From xz=2z−y, we also can get 2z−x−y=xz−x→3z−T=x(z−1). Make the similar equations and multiply them, we get
xyz(x−1)(y−1)(z−1)=(3x−T)(3y−T)(3z−T).
Note that (x−1)(y−1)(z−1)=xyz−(xy+yz+zx)+(x+y+z)−1=xyz−1 and
(3x−T)(3y−T)(3z−T)=27xyz−9T(xy+yz+zx)+T2(3x+3y+3z)−T3=27xyz−9T2+2T3
Thus
xyz(xyz−1)=27xyz−9T2+2T3 or (xyz)2−28xyz=2T3−9T2.(1)
By the similar transformation, xz=2z+y→xz+2x=2z+2x−y→x(z+2)=2T−3y. Make the similar equations and multiply them, side by side, we get
(xyz)2+6(xyz)T+35xyz=18T2−4T3.
On the other hand, xz=2z−y→xyz=2yz−y2. Make the similar equations and multiply them, side by side, we get
3xyz=2(xy+yz+zx)−(x2+y2+z2)=4(xy+yz+zx)−(x+y+z)2=4T−T2.
So we have xyz=34T−T2, then by substituting to equation (1), we get
(34T−T2)2−28(34T−T2)=2T3−9T2(2)
Solving this equation, we have T∈{0,3,7,16}.
1. If T=0, then xyz=0, a contradiction.
2. If T=16, then xyz=−64 and this pair (T,xyz)=(16,−64) does not satisfy equation (2).
3. If T=3, then xyz=1 and by Vieta's theorem, x,y,z are real roots of t3−3t2+3t−1=0, which implies that x=y=z=1.
4. If T=7, we get xyz=−7 and x,y,z are roots of t3−7t2+7t+7=0, this also have three distinct real roots.
Hence, all possible values of T are 3 or 7.