帮忙求一个全微分u=2sin(x+2y-3z)-( x+2y-3z ).z=z(x,y)
求函数u=ln(2x+3y+4z^2)的全微分du
求函数z=x^2y的全微分
已知x::y:z=3:4:5,(1)求x+y分之z的值;(2)若x+y+z=6,求x,y,z.
已知2x+3y-4z=0,3x+4y+5z=0,求x+y+z/(除以)x-y+z的值.
设x+y+z=11求函数u=2x*x+3y*y+z*z的最小值
1.已知x:y:z=4:5:7,求:(一)2x+3y+z/5z; (二)x+y/y+z 非常急,
已知3x-2y-5z=0,2x-5y+4z=0,且x,y,z都不为0,求(3x*x+y*y+4z*z)/(5x*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/2=y/3=z/4,求下列各式 (1)(x+y+z)/x (2)(x-y+2x/(x-y-2z)
证明:(y+z-2x)3+(z+x-2y)3+(x+y-2z)3=3(y+z-2x)(z+x-2y)(x+y-2z).
已知|x+(-2)|+|y+3|+|z|=0,求x+y+z的值.
x=y/z=z/3,x+y+z =12,求2x+3y+4z是多少,