(3)一般情形 11 12 In D=a a i2 n2 nn I 12 In : =an+0+…+00+a2+…+0…0+…+0+an nn 上页(3) 一般情形 n n nn i i in n a a a a a a a a a D            1 2 1 2 11 12 1 = n n nn i i i n n a a a a a a a a a               1 2 1 2 11 12 1 = + 0 + + 0 0 + + + 0 0 + + 0 +