(A1+A2+A3,A1+2A2,9A3) = (A1,A2,A3) KK= 1 1 01 2 01 0 9等式两边取行列式得 |A1+A2+A3,A1+2A2,9A3| = |A||K| = 1*9 = 9.
用detA表示行列式原式=9det(A1+A2,A1+2A2,A3)=9det(A1+A2,A2,A3)=9det(A1,A2,A3)=9*1=9