若2x-3y+z=0,3x-2y-6z=0.若2x-3y+z=0,3x-2y-6z=0,且xyz不等于0,求（x平方＋y平方＋z平方）/（2x平方＋y平方－z平方）的值

若|x+3|+|y-2|+|2×z+1|=0求(x×z-y×z)(y-x+z)的值 证明 ：x/(y+z)+y/(z+x)+z/(x+y)>=3/2其中 x,y,z>0 如果|x+y+z-6|+|2x+3y-z-12|+|2x-y-z|=0求x,y, 若4x-3y-6z=0,x+2y-7z=0,则x+y+z/3x-y+z=? 若x+y+z=3y=2z,则x/x+y+z=? 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+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 x+y+z=6 x+2y+3z=14 y+1=z 若X:Y:Z=5:6:7那么(Y-X):(Y+Z)和(X+2Y+3Z):(3X+2Y+Z) 2x+z=10 x+y-z=4 3x-y-z=0 三元一次方程x+y+z=0 4x+2y+z=3 9x+3y+z=6x+y+z=04x+2y+z=3 9x+3y+z=6 (1)X+Y=15,Y+Z=-6,Z+X=7.(2)X+Y=-14,Y+Z=-7,Z+X=9.(3)X+Y=0,Y+Z=-1,Z+X=-1. 若方程组2x+3y-z=0,x-3y-z=0,则x：y：z=? X+y-z=6;x-3y+2z=0;3x+2y-z=4 x-y+z=0,2x+y-2z=6,3x-y-z=3求解, {x+y-2z=-3 2x+6y+z=2 x+y+z=0