3.设有线性方程组 ) lambda (x)_(1)-(x)_(2)+2(x)_(3)=-3 (x)_(1)+(x)_(2)=-lambda (x)_(1)+lambda (x)_(3)=-2 . ,问λ为何值时,此方程组(1)有唯一解?(2)-|||-无解?(3)有无穷多个解?并在有无穷多个解时用基础解系表出其全部解。(18分)