已知x/2=y/3=z/5,则x+y-2z/x-y=( ) 怎样想和做?
已知2x+5y+4z=15.7x+y+3z=14 则x+y+z=?
已知方程组4x-5y+2z=0 x+2y=3z 则x:y:z
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.
已知x-y+z=0,3x+y-5z=0,则x+y+z/x+2y-3z=?
已知x-y+z=0.3x+y-5z=0,则x+y+z/x+2y-3z=_______
已知x,y,z 大于0,x+y+z=2,求证 xz/y(y+z)+zy/x(x+y)+yx/z(z+x)大于等于2/3
x/2=y/3=z/5 x+3y-z/x-3y+z
已知3x=4y,2y=5z,试求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)
已知,x/2=y/3=z/4,则(2x+y-z)/(3x-2y+z)=?
已知3x-2y-5z=0,2x-5y+4z=0,且x,y,z均不为0,求3x*x+2y*y+5z*z/5x*x+y*y-
已知{x-3y+2z=0 3x-3y-4z+0,则x:y:z=?