急!求-（x-y+z)-2(x-y+z)-3(x-y+z)的值,其中x=2,y= -1 z=3

方程组x+3y-z=17 2x-y+z=16中的y、z同时满足y=z+2,求x、y、z.急! 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. 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 急!求-（x-y+z)-2(x-y+z)-3(x-y+z)的值,其中x=2,y= -1 z=3 求x.y.z. 求x、y、z 数学题(x+y+z-2)^2+(y+z+2-x)^2急求! 1.已知x:y:z=4:5:7,求：（一）2x+3y+z/5z； （二）x+y/y+z 非常急, （x+y+z）(x-y+z)+(y-x+z)(y-x-z)求过程 200分求数学题,急x+y-z=-14x-3y+2z=162x-2y-3z=5求z等于多少 已知x/3=y/5=z/4,求x+y+z/y和x+y-z/y-x的值,2种方法.急等. x+2y=3x+2z=4y+z 求x:y:z (x*x+2)(y*y+4)(z*z+8)=64xyz,求x,y,z 已知 x/(y+z)+y/(z+x)+z/(x+y)=1求 (x*x)/(y+z)+(y*y)/(x+z)+(z*z)/(x+y)=? (y+z)/x=(z+x)/y=(x+y)/z求x+y-z/x+y+z的值 求初二数学题的解.~!急2|X-Y|+`√2Y+Z`+Z的平方- Z + 四分之一求X+Y+Z的值 如果x+y=2z,且x≠y,那么x/(x-z)+y/(y-z)等于( )急