A1+B1A2+B2 Ais Bis 4+B= A21+B21A2+B22 A2、+B2 41+B,A2+B2A+B kA kA2 … kAs kA2 kA= kA kAs A= kA k42… kA、 A 上页 返回              + + + + + + + + + + = r r r r r s r s s s s s A B A B A B A B A B A B A B A B A B A B        1 1 2 2 2 1 2 1 2 2 2 2 2 2 1 1 1 1 1 2 1 2 1 1               = r r r s s s k A k A k A k A k A k A k A k A k A k A        1 2 2 1 2 2 2 1 1 1 2 1               = T r s T s T s T r T T T r T T T A A A A A A A A A A        1 2 12 22 2 11 21 1