maths 2x+3y-z=11 2x+y-5z=8 -2x+7y+z=19 方程组要是正确的!

maths 2x+3y-z=11 2x+y-5z=8 -2x+7y+z=19 方程组 maths 2x+3y-z=11 2x+y-5z=8 -2x+7y+z=19 方程组要是正确的! 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 证明 ：x/(y+z)+y/(z+x)+z/(x+y)>=3/2其中 x,y,z>0 x/2=y/3=z/5 x+3y-z/x-3y+z x+2y=3x+2z=4y+z 求x:y:z x+y/2=z+x/3=y+z/4 x+y+z=27 若x+y+z=3y=2z,则x/x+y+z=? 解下列方程组3x-y+z=3,2x+y-3z=11,x+y+z=123x-y+z=32x+y-3z=11x+y+z=12 2x+y+2z=4,3x-2y+z=11,x+y-2z=-2 2x+y+2z=4 3x-2y+z=11 x+y+2z=-2 3x-2y+2z=3,2x+y-3z=11,x+y+z=12 {x+2y+3z=11,x-y+7z=10,x+3y+2z=2 x+2y+3z=14 2x+y+z=7 3x+y+2z=11 3x+2y+z=9,x+y+2z=0,2x+3y-z=11 3x-y+2z=3 2x+y-3z=11 x+y+z=12 x+2y+4z=17 2x+y+z=7 3x+y+2z=11