2.求x1，x2, x3, x4,使Z＝－3x1+4x2-2x3+5x4达到最小
满足
｛4x1-x2+2x3-x4=-2 x1+x2+2x3-x4≤14 -2x1+3x2-x3+2x4≥2 x1≥0,x2≥0,x3≥≥0≥,x4 ≥无符号限制

｛-4x1+x2-2x3+(x5-x6)=2 x1+x2+2x3-(x5-x6)+x7=14 -2x1+3x2-x3+2(x5-x6)-x8=2 x1≥0,x2≥0,x3,x5,x6,x7,x8≥0