z=x^3+y^3-3xy^2,求二阶偏导数∂z/∂x我看得懂,但∂^2z/∂x∂y=-6y是怎么求的?现在自学偏导数,看得有点昏,请问和导数有什么区别呢?什么时候对x求导什么时候又对y求导?那∂^2z/
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若|x-3|+|y+2|+|2z+1|=0,求(xy-yz)(y-x+z)
z=x^2-xy+y^3 求全微分dz
分式题:xy=x+y,yz=2(y+z),zx=3(z+x),求xyz/(xy+yz+xz)xy=x+y,yz=2(y+z),zx=3(z+x),求xyz/(xy+yz+xz)
24xy^2z^2(x+y+z)-32xyz(z-x-y)^2+8xyz^3(z-x-y)
24xy^2z^2(x+y+z)-32xyz(z-x-y)^2+8xyz^3(z-x-y)
(x+y-xy)/(x+y+2xy)=(y+z-2yz)/(y+z+3yz)=(z+x-3zx)/(z+x+4zx),且2/x=3/y=1/z,则xyz=?
已知(x+y-xy)/(x+y+2xy)=(y+z-2yz)/(y+z+3yz)=(z+x-3zx)/(z+x+4zx),且2/x=3/y-1/z,则xyz=?
已知4x-3y=6z 2x+4y=14z 求2xy/x^+y^
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已知3x-y+2z=x+2y+3z=0,求(3x^-xy+2y^)/(2x^+4xy+y^)值?
已知XY+X/X+Y+1=2 XZ+2X/X+Z+2=3 (Y+1)(Z+2)/Y+Z+3=4 求X+Y+Z的值已知(XY+X)/(X+Y+1)=2 (XZ+2X)/(X+Z+2)=3 [(Y+1)(Z+2)]/(Y+Z+3)=4 求X+Y+Z的值
已知2x-3y-z=0,x+3y-14z=0(z≠0),求x^2+3xy/y^2+z^2
已知2x-3y-z=0 x+3y-14z=0(z≠0) 求x^+3xy/y^2+z^
x+3xy=z 求X/Y
已知xy/x+y=3,yz/y+z=2,zx/z+x=1,求y的值
若|x-3|+|y+z|+|2z+1|=0,求XY-YZ的值
若|x-3|+|y+z|+|2z+1|=0,求xy-yz的值
解三元方程!(1) xy=997003-z (2)x=999z (3) x-y=z