x-y=8 (1)
xy+z^2=-16 (2)
由(1) y=x-8
代入(2) x^2-8x+16+z^2=0
△=64-64-4z^2=-z^2>=0
z=0
方程变成：x^2-8x+16=0
x=4 y=-4
∴ x=4 y=-4 z=0