设(x+y)/2=(y+z)/3=(z+x)/4=kx+y=2ky+z=3kx+z=4k1式+3式2x+y+z=6k2x+3k=6k2x=3kx=3k/2代入1式得y=k/2代入3式得z=5k/2∵x+2y+z=12∴3k/2+2*k/2+5k/2=12k=12/5x-2y+z=3k/2-2*k/2+5k/2=3k=36/5