已知3X-4Y-Z=0,2X+Y-8Z=0.求：（1）X+2Y-7Y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4x-3y+z=0,x+2y-8z=0,xyz不等于0,求x+y-z/x-y+2z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 已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,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{x-3y+2z=0 3x-3y-4z+0,则x:y:z=? 已知x+4y-3z=0,4x-5y+2z=0,则x：y：z 已知{x-5y+2z=0 3x-5y-4z=0,求x：y:z 已知方程组4x-5y+2z=0 x+2y=3z 则x:y:z 已知3x-4y-z=0,2x+y-8z=0,且z≠0,则x：y：z=（ ） 已知：4x-5y+2z=0 x+4y-3z=0则：(x*x+y*y+z*z)/(x*y+y*z+z*x)=____. 已知方程组4x-3y-2z=0,x-3y+z=0,z≠0求x/z,y/z的值 已知x+2y-4z=0,3x-y-z=0,则3x+2y+z/x+2y+z= 已知4x-3y-6z=0,x+2y-7z=0,求5x+2y-z/2x-3y-10z 已知4X-3y-3z=0 X-3y-Z=0求3X-2Z+Y/-x+y+Z的值 已知4X-3Y-3Z=0和X-3Y-Z=0 求3x-2z+y：-x+y+z的值