已知3x－y+2z=x+2y+3z=0,求（3x^－xy+2y^)/(2x^+4xy+y^)值?

已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,求x,y,z 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,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 已知z、y、z同时满足x+3y-5z=0,2x-y-3z=0,求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. 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 证明 ：x/(y+z)+y/(z+x)+z/(x+y)>=3/2其中 x,y,z>0 已知：x+2y-3z=0,3x-2y+z=0,则x：y：z= 已知 3x-y+2z=0 2x+y-3z=0,求x :y :z. 已知{x-3y+2z=0 3x-3y-4z+0,则x:y:z=? 已知x-2y+3z=0,x-3y+4z=0,则x:y:z= 已知2x-y-z=0,3x+4y-2z=0,则x：y：z=? 已知（1）X-Y+Z=0 (2)X+2Y-3Z=0 求X:Y:Z 已知x+4y-3z=0,4x-5y+2z=0,则x：y：z 已知｛2x-y-z=0,3x-9y+z=0求1,x:y:z 已知{x-5y+2z=0 3x-5y-4z=0,求x：y:z 已知｛X-Y+Z=0,X+2Y-3Z=0求X：Y：Z的值