已知x+7y+8z=3 3x-y+2z=5 求x+y+2z的值.已知x+7y+8z=33x-y+2z=5求x+y+2z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.. 已知关于x y z的方程组2x-3y+5z=7 x+2y-3z=8,则4x+y-z= 已知:x+y+z=0,5x-3y-z=0,求:5x-y+z/2x+8y+7z 的值 已知实数x y z满足x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3,求x+y+z的值 已知实数x y z满足x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3,求x+y+z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2x+5y+4z=6 3x+y-7z=-4求x+y-z {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 已知x+4y+3z=3x-2y-5z=0,求x+2y-z/2x-3y+7z的值 已知4x-3y-6z=0,x+2y-7z=0,求5x+2y-z/2x-3y-10z 已知有理数x、y、z满足条件|x-z-2|+(3x-6y-7)^2+|3y+3z-4|=0,求x、y、z 已知有理数x,y,z满足|x-z-2|+|3x-6y-7|+(3y+3z-40)^2=0,求x,y,z的值 已知：4x-3y-6z=0,x+2y-7z=0.求出x-y+z÷x+y+z=? 已知4x-3y-6z=0,x+2y-7z=0,则x-y+z/x+y+z=_________ 已知4x-3y+6z=0 x+2y-7z=0 则x-y+z/x+y-z=? 已知,方程组:4x-3y-7z=0 x+2y=10z 则(x-y+z)÷(x+y+z)=—— 已知{4x-3y-6z=0、x+2y-7z=0,则x-y+z：x+y+z=