若x：y：z=3：5：7,3x+2y-4z=9,则x+y+z的值为（ ）.A.-3 B.-5 C.-7 D.-15

若X:Y:Z=5:6:7那么(Y-X):(Y+Z)和(X+2Y+3Z):(3X+2Y+Z) 若3x+7y+z=5,4x+10y+z=3,则x+y+z=? (4x-2y-z)-{5x-[8y-2z-(x-2y)]-x-(3y-10z)}=? 若x/2=y/3=z/4,则3x-2y+5z/x+y+z= 2x+5y+4z=6,3x+y-7z=-4,x+y-z=? 若x/3=y/4=z/5,求x+y+z/3x-2y+z的值. 已知2x+5y+4z=6 3x+y-7z=-4求x+y-z X-Y-Z=0 X+Y-3Z=4 2X-5Y+7Z=21 3x+7y+4z=35,x+5y+2z=40,x+y+z=( ) {x+y+z=1 {x+3y+7z=2 {x+5y+19z=4 5x+3y+2z=2011 4x+6y+7z=2012 求x+y+z 若x+2y-9z=0,x-2y+5z=0,(x.y.z≠=0)求2x平方+3y平方+7z平方/x平方-4y平方+4z平方 1.{x:y:z=3:4:5 2x+3y-5z=-142.{x-y-z=-1 3x+5y+7z=11 4x-y+2z=-13.{x+y=1 x+z=0 2x+y+2z=44.{x-y+z=-3 2x-y-z=-2 -3x+y+z=-15.{x-y+z=-3 3x+y-4z=6 2x+y-z=36.{x-2y+5z=16 2x+y-5z=7 2x-y+z=38 {5x-3y+z=2{5x+2y-4z=3{-5x+y-z=2 {x-y-z=-1{3x+5y+7z{4x-y+2x=-1 已知x+4y+3z=3x-2y-5z=0,求x+2y-z/2x-3y+7z的值 若4x-3y-6z=0,x+2y-7z=0,则x+y+z/3x-y+z=? 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