(3)一般情形 n D=ai ai2 n 2 n 1 In =an1+0+…+00+a2+…+0…0+…+0+an 28 (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 +