已知x:y:z＝1:2:3 且2x+y-3z＝-15 x值为?

已知x:y:z＝1:2:3 且2x+y-3z＝-15 x值为? 已知x,y,z都是正数,且xyz=1,求证：x^2/(y+z)+y^2/(x+z)+z^2/(x+y)≥3/2 已知有理数x,y,z,且|x-3|＋2|y+1|+（2z+1）²＝0,求x+y+z的相反数的倒数. 已知x:y:z=2:3:4,且x-y+z=36,求x+y+z的值. 已知x:y:z=2:3:4且x+z-y=36求x+y+z的值 已知x:y:z=2:3:4,且x+z-y=36.求x+y+z的值 已知x:y:z=2:3:4,且x+y+z=18.求x、y、z的值. 已知方程组{X+Y-7Z=0(1)3X-2Y-Z=0(2)且Z不等于0求X:Y:Z 1 已知x+y/y=7/3 求x+y/x-y等于什么2 若x+4/3=y+3/2=z+8/4 且x+y+z=12 求x、y、z的值 已知x,y,z∈R+,且x+y+z=3,求证：x^2/（y^2+z^2+yz）+y^2/(x^2+z^2+zx）+z^2/(x^2+y^2+xy)≥1 已知（x+y-xy）/(x+y+2xy)=(y+z-2yz)/(y+z+3yz)=(z+x-3zx)/(z+x+4zx),且2/x=3/y-1/z,则xyz=? 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/3=z/5.且x+y-2z不等于0.求2x+3y-z/x+y-2z的值是多少 已知x+y/2=y+z/3=z+x/4,且x+2y+z=12,求x-2y+z的值 已知x/2=y/3=z/4,且x+y+z不等于0,求2x+3y-4z/x+y+z的值 已知方程组{2x-3y+z=0 且x*y*z不等于0 求 x：y：z {3x-2y-6z=0 已知x/2=y/3=z/4,且x+y+z不等于0,求2x+3y-4z/x+y+z的值