If x = `sum_(n=0)^oo` an, y = `sum_(n=0)^oo` bn, z = `sum_(n=0)^oo` (ab)n, where |a|, |b| <1, then
xyz = x+y+z
xz+yz = xy+z
xy+yz = xz+y
xy+xz = yz+x
i could not figure it out. could you please explain it.