求函数z=x^3-y^3+3x^2+3y^2-9x的极值

设x+y+z=11求函数u=2x*x+3y*y+z*z的最小值 已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,求x,y,z 设函数z=z(x,y),由方程z=e^(2x-3z)+2y确定,求∂z/∂x,∂z/∂y x+2y=3x+2z=4y+z 求x:y:z 设方程2sin(x 2y-3z)=x 2y-3z确定函数z=z(x,y),求Zx,Zy 已知实数x y z满足x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3,求x+y+z的值 已知实数x y z满足x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3,求x+y+z的值 设函数z=z(x,y)由方程x^2+y^3-xyz^1=0确定,求z/x,z/y 如果|x+y+z-6|+|2x+3y-z-12|+|2x-y-z|=0求x,y, 分式加减的几道题目求速度1 .(x+y)²/（x-z)(y-z) - (y+z)²/（x-z)(y-z) = 2.2x+3y/x-y+2y/y-x-3y/x-y= 求二元函数z=y^3-x^2+4x-3y+1的极值 求函数z=e^(x+ y) +3x^(2)y^(2) 的全微分 x=y/z=z/3,x+y+z ＝12,求2x+3y+4z是多少, 设|x|-|y|+|z|=|x+y+z|,且|x+y|=4,|y+z|=5,|y|=3,求(x-y-z)^2的值 若|x+3|+|y-2|+|2×z+1|=0求(x×z-y×z)(y-x+z)的值 x+y+z=35 2x-y=5 y/3=z/2 求x,y,z x+y-z=3 y+z-x=5 z+x-y=7 求x,y,z 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y)