X +2y +3z =5 2X +3y +z =13 3X +y +2z =12 用加减消元法X +2y +3z =52X +3y +z =133X +y +2z =12用加减消元法!

x/2=y/3=z/5 x+3y-z/x-3y+z 已知x-y/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. 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 (4x-2y-z)-{5x-[8y-2z-(x-2y)]-x-(3y-10z)}=? (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuaihuajian 1.（x+y-z)+(x-y+z)-(x-y-z) 2.2x-(3x-2y+3)-(5y-2) 设|x|-|y|+|z|=|x+y+z|,且|x+y|=4,|y+z|=5,|y|=3,求(x-y-z)^2的值 x+y=5 2x+3y-z=9 x-y+z=4 已知x/y+z=y/x+z=z/x+y,分式(x+2y+3z)/(2x+5y-2c)有意义时的值 x+y+z=35 2x-y=5 y/3=z/2 求x,y,z (4x-2y-z)-{5x-[8y-2z-(x+y)]-2(3y-10z)}=?好难啊 2(x+y-z)-3(x-y+z)-5(x+y-z)+6(x-y+z) 计算 证明 ：x/(y+z)+y/(z+x)+z/(x+y)>=3/2其中 x,y,z>0 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=? 若X:Y:Z=5:6:7那么(Y-X):(Y+Z)和(X+2Y+3Z):(3X+2Y+Z)