已知2x+5y+4z=15.7x+y+3z=14 则x+y+z=?要有为什么

已知2x+5y+4z=15.7x+y+3z=14 则x+y+z=? 已知(x+2y)/3=(y+3z)/4=(z+5x)/5,则x:y:z= 已知x+2y/3=y+3z/4=z+5x/5,则x:y:z=? 已知x+2y/3=y+3z/4=z+5x/5,则x:y:z= 已知{x-5y+2z=0 3x-5y-4z=0,求x：y:z 已知X:Y:Z=3:4:5,求4X+3Y-2Z/X+Y+Z的值 已知2x+5y+4z=6 3x+y-7z=-4求x+y-z 已知x+4y-3z=0,4x-5y+2z=0,则x：y：z 已知x+4y=3z,4x-5y=-2z,则x:y:z 已知方程组4x-5y+2z=0 x+2y=3z 则x:y:z 已知x/4=y/5=z/6 求x+y+z/3x-2y+z的值 已知x/4=y/5=z/6,求x+y+z/3x-2y+z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-5y+2z=0 x+4y-3z=0则：(x*x+y*y+z*z)/(x*y+y*z+z*x)=____. 已知x+4y+3z=3x-2y-5z=0,求x+2y-z/2x-3y+7z的值 已知关于x y z的方程组2x-3y+5z=7 x+2y-3z=8,则4x+y-z= 已知4x-3y-6z=0,x+2y-7z=0,求5x+2y-z/2x-3y-10z 已知3x+4y+5z=0,2x+3y-4z=0,求(x+y+z)/(x-y+z)