设 1996x^3=1997y^3=1998z^3,xyz>0,(1996x^2+1997y^2+1998z^2)的立方根=1996的立方根+1997的立方根+1998的立方根,求1/x + 1/y + 1/z 的值.1996x^3 是指 1996倍的（x的立方）

设x.y满足条件y>=0.X-Y+1>=0.x+y-3 设x,y满足约束条件{x>=0,y>=x,4x+3y 设x,y满足约束条件x>=0 y>=x 4x+3y 设自然数x,y满足x小于y,x^3+19y=y^3+19x,则x+y等于? 设函数y=(1+x^3)^(cosx),求y' 设x,y满足x＋3y＋|3x－y|＝19,2x＋y＝6则X= Y= 设变量X,Y满足约束条件{X-Y+3>=0,X+Y>=0,-2 设变量x,y满足约束条件:x-y+3>=0 x+y>=0 -2 设不等式组x+y-2>=0,x-3y+6>=0,x-y 设X+Y=K,且X,Y满足不等式组 X-3Y 设y=3^x+core^x,求dy 设正实数x,y满足x^3+y^3=x-y,求证：x^2+4y^2 设实数X,Y满足2X+Y-2>=0,X-2Y+4>=0,3X-Y 设变量x,y满足约束条件x-y>=-1,x+y>=1,3x-y 设实数x,y满足方程组①x-y-2=0 ③2y-3 设A={(x,y)/x+y 设M={(x,y)||x|+|y| 设不等式组{x>=0,x+3y>=4,3x+y