若x+2y-9z=0,x-2y-5z=0(xyz=0)求x^2-4y^2+9z^2分之2x^2+3y^2+7z^2的值

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^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 若|x+3|+|y-2|+|2×z+1|=0求(x×z-y×z)(y-x+z)的值 2x+3y-z=9,x+y+z=15,5x-4y-z=0 若xyz≠0且4(x/z)-5(y/z)=-2,(x/z)+4(y/z)=3,求x:y:z 9x-5y+z=-6 9x+y-2z=3 -9x+3y-5z=0 求x y z 若x+2y-9z=0,x-2y+5z=0,(x.y.z≠=0)求2x平方+3y平方+7z平方/x平方-4y平方+4z平方 证明 ：x/(y+z)+y/(z+x)+z/(x+y)>=3/2其中 x,y,z>0 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 已知z、y、z同时满足x+3y-5z=0,2x-y-3z=0,求x:y:z x>=y>=z>0,求证：x^2*y/z+y^2*z/x+z^2*x/y>=x^2+y^2+z^2 已知(x+y+z)^2=x^2+y^2+z^2,证明x(y+z)+y(z+x)+z(x+y)=0 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 若有理数x,y,z满足(x-1)的2016次方+|2x-y|+lx-3z|=0,求3x-5y-9z的值 1.若3x-2y+z=2;3x+2y+5z=4,求x+22.若x-3y+z=0;3x-3y-4z=0,求x:y:z