⑩天掌 Teaching Plan on Advanced Mathematics 1≤x<1 故Ω x≤ys 2 x2+2y z≤2-x =,.小2(x,, tianjin Polytechnic univerityTianjin Polytechnic University Teaching Plan on Advanced Mathematics 故 ：      +   − − −   − −   2 2 2 2 2 2 2 1 1 1 1 x y z x x y x x , ( , , ) . 1 1 2 2 1 1 2 2 2 2 −  2  − + − − −  = x x y x x I dx dy f x y z dz