解: 系数矩阵 A =1 2 1 -21 -1 -5 70 1 2 -3r2-r11 2 1 -20 -3 -6 90 1 2 -3r1-2r3,r2+3r31 0 -3 40 0 0 00 1 2 -3基础解系为: a1=(3,-2,1,0)', a2=(4,-3,0,-1)'通解为: c1a1+c2a2, c1,c2 为任意常数.
