已知3x-2y-5z=0,x+2y-7z=0,xyz≠0,求（x^2-2y^2+z^2)/yz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-6z=0,x+2y-7z=0,求5x+2y-z/2x-3y-10z 已知x+4y+3z=3x-2y-5z=0,求x+2y-z/2x-3y+7z的值 已知:x+y+z=0,5x-3y-z=0,求:5x-y+z/2x+8y+7z 的值 已知z、y、z同时满足x+3y-5z=0,2x-y-3z=0,求x:y:z 已知x+2y-3z=0,5x-6y+7z=1;则x:y:z=?把“5z-6y+7z=1”改成“5x-6y+7z=0” 已知x,y,z满足方程组x-2y+z=0 7x+4y-5z=0,且z不等于0,2x²-3y²+z²/y²-2z²的值为? 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^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,z,满足方程组x-2y+z=0,7x+4y-5z=0 已知{x-5y+2z=0 3x-5y-4z=0,求x：y:z 已知x+4y-3z=0,4x-5y+2z=0,则x：y：z 已知方程组4x-5y+2z=0 x+2y=3z 则x:y:z 已知2x+5y+4z=6 3x+y-7z=-4求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x+2y-7z=0,3x-5y+z=0,用z的代数式分别表示x,y,则y= x= 已知x+y-7z=0 x-2y+5z=0(xyz不等于0）,求x+2y-z/y-2x+12z