x+3y-7z=4x+3y=7z+4 (1)2x+y+z=32x+y=3-z (2)(1)×2-(2)5y=15z+5y=3z+1,代入(2)x=(3-z-y)/2=(3-z-3z-1)/2=1-2zx≥0 1-2z≥ 0 z ≤1/2y≥0 3-z≥0 z≤3综上,得z≤1/2,又z为非负整数,z=0x=1-2z=1 y=3z+1=1x=1 y=1 z=0
