若x,y>0 X+3Y=z 则1/x+1/y的最小值是多少?X+3Y=1 打错了！不好意思

若|x+3|+|y-2|+|2×z+1|=0求(x×z-y×z)(y-x+z)的值 三元一次方程组题目x+y-z=11 y+z-x=5 x-y+z=1x+y=4 y+z=3 x+z=5若已知x-3y+2z=0 2x+3y-8z=0, 且xyz≠0,则x:y:z= 若x:y:z=3:2:1,则x+2y-z/2x-y+z= 已知 x/(y+z)+y/(z+x)+z/(x+y)=1求 (x*x)/(y+z)+(y*y)/(x+z)+(z*z)/(x+y)=? 若|x+1|+（y-2）方+|x+z-3|=0,则x+y+z的值是? 若x+y+z=3y=2z,则x/x+y+z=? 若有理数x,y,z满足等式：（x-1)的平方+（2x-y)的平方+｜3x-z｜=0,求x+y+z的值 若有理数x,y,z满足等式：（x-1)^2+(2x-y)^2+|3x-z|=0,求x+y+z的值 若有理数x、y、z满足等式(x-1)^2+(2x-y)^4+|x-3z|=0,求x、y、z的值 若有理数x,y,z满足(x-1)的平方+|2x-y|+|x-3z|=0,求x+y+z的值 若|x-3|+|y+2|+|2z+1|=0,求(xy-yz)(y-x+z) 若实数X,Y满足{ x-y-1≤0,x+y-3≤0,x≥1,则函数z=2x-y的最大值 若变量x y满足约束条件x+y≤5 x-y≤-1 x≥0 则z=3x-2y的最小值 若x:y=2:3,y:z=1:2,且x+y+z=55,则y=? 方程组 (1) x+2y-3z=12 x-3y+2z= - 13 x-y-z=0 (2) x+ y=z 5x-y+z=18 2x+5y+3z= -1 (1)X+Y=15,Y+Z=-6,Z+X=7.(2)X+Y=-14,Y+Z=-7,Z+X=9.(3)X+Y=0,Y+Z=-1,Z+X=-1. 已知xyz≥0,x+y+z=1,化简x（2y-z）/(1+x+3y)+y(2z-x) /(1+y+3z) +z(2x-y)/(1+z+3x) 设f(x,y,z)=e^x*y*z^2,其中z=z(x,y)是由x+y=z+x*e^(z-x-y)确定的隐函数,则f'x(0,1,1)=