x+y=8 y+z=12 x+z=10 x+y+z=

(x+y-z)(x-y+z)= X+Y+Z=? f(x,y,z,w)=x*(x+y)*(x+y+z)*(x+y+z+w) 解方程组{x(x+y+z)=6,y(x+y+z)=12,z(x+y+z)=18 若{x+3y+10z=0 则 (x+y-z)/(x-y+z) x y z x+y--- = --- = ---- ----y+Z z+x x+y ,求 z 的值 .求 x+y---- 已知x+y-z/z=x-y+z/y=-x+y+z/x,且xyz不等于0,求分式[(x+y)(x+z)(y+z)]/xyz 若z分之x+y+z=y分之x-y+z=x分之-x+y+z,求xyz分之(x+y)(y+z)(z+x) y+z÷x=Z+X÷y=X+Y÷z,X+Y+Z不等0求X+Y-Z÷X+Y+z值 (x+y-z)/z=(y+z-x)/x=(z+x-y)/y 求(x+y)(y+z)(z+x)/xyz x分之y+z=y分之z+x=z分之x+y(x+y+z不等于0）,求x+y+z分之x+y-z 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y)