r=√(x^2+y^2+z^2),求x的偏导数?

已知x,y,z∈ R,x+2y=z+6,x-y=3-2z,求x^2+y^2+z^2的最小值. r=√(x^2+y^2+z^2),求x的偏导数? 已知：x^2/(z+y)+y^2/(x+z)+z^2/(x+y)=0,求x/(z+y)+y/(x+z)+z/(x+y)的值. x^2/(z+y)+y^2/(x+z)+z^2/(x+y)=0,求x/(z+y)+y/(x+z)+z/(x+y)的值 xyz∈R+且 x+2y+3z=36求 1/x +2/y +3/z的最小值 已知x,y,z∈R+,3x+2y+z=6 求xyz的最大值 已知x,y,z属于R,且x+y+z=6,求x^2+y^2+z^2的最小值 已知X,Y,Z∈R+,且1/X+2/Y+3/Z=1.求X+Y/2+Z/3的最小值 已知x,y,z属于R+,x+y+z=3,(1)求1/x+1/y+1/z的最小值,（2）证明：3 2|X-Y|+√2Y+Z+Z²-Z+1/4=0求X+Y+Z的值 已知：x,y属于R,求Z=x^2+4y^2-6x+8y的最小值. 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 已知x、y、z满足方程组：x+y-z=6；y+z-x=2；z+x-y=0 求x、y、z的值 已知X.Y.Z满足方程组,X+y-Z=6y+z-x=2z+x-y=0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 若|x+3|+|y-2|+|2×z+1|=0求(x×z-y×z)(y-x+z)的值 |x-2|+√x-2y+z^2-2z+1=0,求3x-y+z的值 1 设x、y、z属于R且（x-1)^2/16+(y+2)^2/5+(z-3)^2/4=1,则x+y+z的最小值为?2 已知正数x,y,z满足x+y+z=xyz,且不等式1/（x+y) + 1/(y+z)+ 1/(z+x)小于等于k恒成立,求k的取值范围