先将原题转化为标准模式，令z=-f，添加松弛变量x3,x4
max z = 2x1+3x2+0x3+0x4
st. x1 + x2 + x3 = 2
4x1 +6x2 + x4 = 9
建立初始单纯形表
cj 2 3 ...