x+y+z=15 4x+2y+3z=56

试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) x=y/z=z/3,x+y+z ＝12,求2x+3y+4z是多少, x+2y=3 x+y+z=36 2x+y+z=15 2y=3z x-y=1 x+2y+z x-z=-1 2x+z-y=1 ｛4x-9z=17 3x+y+15z=18 x+2y+3z=2 4X-9Z=17 3X+Y+15Z=18 X+2Y+3Z=2 {4x-9z=17{3x+y+15z=18{x+2y+3z=2 4x-5z=17 3x+y+15z=18 x+2y+3z=2 x/2=y/3=z/5 x+3y-z/x-3y+z x+y+z=2 ① 2x+3y+z=38 ① x+y=3 3x-y-4z=5 ② 3x+4y+2z+56 ② y+z=5 (x+y-z)(x-y+z)= 1.x+y=16,y+z=12,z+x=102.3x-y+z=4,2x+3y-z=12,x+y+z=63.x+y+z=6 (1)3x+4y=15 2y-z=2 x+2z=9 (2) x+y+z=8 2x+3y-z=6 3x-y+z=8 (3)