x+2y-9z=0,x-yx-5z=0（x y z≠0）求代数式 (2x^2-3y^2+7x^2)/(x^2-4y^+9z^2)=

已知x,y,z 大于0,x+y+z=2,求证 xz/y(y+z)+zy/x(x+y)+yx/z(z+x)大于等于2/3 x-yx-=0,y+z=70,x-z=5的方程组怎么解? x+2y-9z=0,x-yx-5z=0（x y z≠0）求代数式 (2x^2-3y^2+7x^2)/(x^2-4y^+9z^2)= 已知x-y/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. 已知x+4y+3z=3x-2y-5z=0(xyz不等于0),求xy+yx+2xz/2x平方-3y平方+7z平方 已知X的2次方+Y的2次方+Z的2次方-XY-YX-ZX=0求证X=Y=Z 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 2x+3y-z=9,x+y+z=15,5x-4y-z=0 xyy-zz=yx 问x.y.z分别是多少 9x-5y+z=-6 9x+y-2z=3 -9x+3y-5z=0 求x y z 已知x-y=a,z-y=10,则代数式x^2+y^2+z^2-xy-yx-zx 三元一次方程解 1.{x+y-z=5 {3x+2y+z=2 {2x-2y+z=-31.{x+y-z=5 2.{9x-5y+x=-6 3.{x-y=3 4.{x+y=3 5.{4x-2y+z=7{3x+2y+z=2 {9x+y-2z=3 {x+z=7 {y+z=4 {2x-y-3z=28{2x-2y+z=-3 {-9x+3y-5z=0 {y-z=6 {z+x=5 {x+y-2z=13 若x,y,z>0且满足x²+xy+y²=49,y²+yx+z²=36,z²+xz+x²=25,求x+y+z的值 ∫∫∫(2xy^2+2yx^2+z)dv,其中,Ω={(x,y,z)|x^2+y^2+z^2≤2z}如题 解方程组2X+YX^2=Y 2Y+ZY^2=Z 2Z+XZ^2=X 已知4分之1x=5分之1y=6分之1z求x：yx：y：z 证明 ：x/(y+z)+y/(z+x)+z/(x+y)>=3/2其中 x,y,z>0