3个3维向量线性相关的充要条件是它们构成的行列式等于0行列式a 1 11 a -11 -1 a= r3+r1a 1 11 a -1a+1 0 a+1= c1-c3a-1 1 1 2 a -1 0 0 a+1= (a+1)[a(a-1)-2]= (a+1)(a^2-a-2)= (a+1)(a-2)(a+1)所以 a=2 或 -1.