X/2=y/3=z/5和x+y+z=20的方程组怎么解{x/2=y/3=z/5;x+y+z=20}怎么解这个方程?

x/2=y/3=z/5 x+3y-z/x-3y+z 若X:Y:Z=5:6:7那么(Y-X):(Y+Z)和(X+2Y+3Z):(3X+2Y+Z) 已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,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-y/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. x+y-z=5,2x+3y+z=10,x-2y-z=20求方程组 x+y-z=5 2x+3y+z=10 x-2y-z=20 速解, 2分之x=3分之y=5分之z x+y+z=20 求x,y,z x+2y+3z=20,x+3y+5z=31,求x+y+z的值 求{x+y-z=5；2x+3y+z=10；x-2y-z=20中x、y、z的值, (4x-2y-z)-{5x-[8y-2z-(x-2y)]-x-(3y-10z)}=? x+y-z=3 y+z-x=5 z+x-y=7 求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. 证明 ：x/(y+z)+y/(z+x)+z/(x+y)>=3/2其中 x,y,z>0 {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 解方程组x+y-z=5和2x+3y+z=10和x-2y-z=20 x+2y+3z=23 y-z=5 x+2z=10 (x+y-z)(x-y+z)=