用定义设k1(a1+a2)+k2(3a2+2a3)+k3(a1-2a2+a3)=0重新分组:a1(k1+k3)+a2(k1+3k2-2k3)+a3(2k2+k3)=0因为a1,a2,a3线性无关,所以有方程组:k1+k3=0;k1+3k2-2k3=0;2k2+k3=0.行列式:10113-2021不等于0,所以方程只有零解,即k1,k2,k3都等于0,所以向量组a1+a2,3a2+2a3,a1-2a2+a3线性无关.