如果2x=y+z 3x+2y-12z=0且z≠0,求（2z²+3xy+y²）/（y²+z²）的值学习指导上的题

如果|x+y+z-6|+|2x+3y-z-12|+|2x-y-z|=0求x,y, 如果2x-3y=z x+3y-14z=0 求x:y:z 快, 证明 ：x/(y+z)+y/(z+x)+z/(x+y)>=3/2其中 x,y,z>0 如果,根号x-3+| y-2 |+z^2=2z-1 求 （x+z)^y 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) 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 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 如果x=3y,z=x/2,那么(x-y+z)/(x+y+z)=多少? 方程组 (1) x+2y-3z=12 x-3y+2z= - 13 x-y-z=0 (2) x+ y=z 5x-y+z=18 2x+5y+3z= -1 X=3z X+y+z=12 X+2y-2z=10 2x+z=10 x+y-z=4 3x-y-z=0 x=y/z=z/3,x+y+z ＝12,求2x+3y+4z是多少, 若|x+3|+|y-2|+|2×z+1|=0求(x×z-y×z)(y-x+z)的值 如果x+4/3=y+z/2=z+8/4,且x+y+z=12,求x,y,z的值. 如果x/2=y/3=z/4,且x+y+z=18,那么x+y-z=?