a1 D ;2 2 2 2 2 证明:D=∑(1)an…(an+b2) =∑(-1) +∑(-1) 第二章行列式第二章 行列式 11 12 1 1 1 2 2 1 2 n i i i i in in n n nn a a a D a b a b a b a a a = + + + 11 12 1 11 12 1 1 2 1 2 1 2 1 2 n n i i in i i in n n nn n n nn a a a a a a a a a b b b a a a a a a = + 证明： ( ) ( ) ( ) 1 2 1 1 1 n i i n j j j D a a b a j ij ij nj  = − +  ( ) ( ) ( ) 1 2 1 2 ( ) 1 1 1 1 1 1 n n i n i n j j j j j j j ij nj j ij nj a a a a b a   = − + −  