令两方程Z相等得母线平行Z轴的柱面:16-(2x²+y²)=y²-x²,即 x²/16 +y²/8=1;
令两方程y相等得母线平行y轴的柱面:16-(2x²+z2)=x²+z²,即 x²/(16/3) +z²/8=1;