若2x+y-3z=1,3x+2y+z=5,x、y、z都是非负数,设m=3x+y-7z,求m的取值范围.

若|x+3|+|y-2|+|2×z+1|=0求(x×z-y×z)(y-x+z)的值 x/2=y/3=z/5 x+3y-z/x-3y+z 若x+y+z=3y=2z,则x/x+y+z=? 已知x:：y：z=3：4：5,(1)求x+y分之z的值；（2）若x+y+z=6,求x,y,z. {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 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/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. 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) 方程组 (1) x+2y-3z=12 x-3y+2z= - 13 x-y-z=0 (2) x+ y=z 5x-y+z=18 2x+5y+3z= -1 x+Y+Z=1 X+3Y+7Z=-1 X+5Y+8Z=2x+Y+Z=1X+3Y+7Z=-1X+5Y+8Z=2 若x/2=y/3=z/4,则3x-2y+5z/x+y+z= 若x/3=y/2=z/5,则2x-3y-z/x-y+z= {x+y+z=1 x-2y+3z=5 2x-3y-3z=-8 2x-y+3z=3 {3X+Y-2Z=-1 X+Y+Z=5