z=x+2y+f(3x-4y),z ▏y=0时=x^2,求偏导Z/偏导x和z对y的偏导2/3(3x-4y) 和 10/3-8/9(3x-4y)

x+2y=3x+2z=4y+z 求x:y:z x+y/2=z+x/3=y+z/4 x+y+z=27 分解因式:f(x,y,z)=x^2(y-z)+y^2(z-x)+z^2(x-y) 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) 已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,求x,y,z (4x-2y-z)-{5x-[8y-2z-(x-2y)]-x-(3y-10z)}=? x=y/z=z/3,x+y+z ＝12,求2x+3y+4z是多少, 2x+z=10 x+y-z=4 3x-y-z=0 设|x|-|y|+|z|=|x+y+z|,且|x+y|=4,|y+z|=5,|y|=3,求(x-y-z)^2的值 f(x,y,z)=(x^2+y^2)^0.5+z^1.5,求 ∂f(x,y,z)/∂y 一道函数不等式题求出所有这样的函数f:R-R,使得对于一切x,y,z∈R,有f(x+y)+f（y+z）+f(x+z)=3f(x+2y+3z)f(x+y)+f（y+z）+f(x+z)=3f(x+2y+3z)改为f(x+y)+f（y+z）+f(x+z)≥3f(x+2y+3z) (4x-2y-z)-{5x-[8y-2z-(x+y)]-2(3y-10z)}=?好难啊 证明 ：x/(y+z)+y/(z+x)+z/(x+y)>=3/2其中 x,y,z>0 3x-y+z=4,2z+3y-z=12,x+y+z=6的解 x+y=5 2x+3y-z=9 x-y+z=4 {2x+y=10 {x-y+z=4 {3x-y-z=0 x/2=y/3=z/5 x+3y-z/x-3y+z 若x+y+z=3y=2z,则x/x+y+z=?