隔離位仁兄條式是對,但中間計錯了少許.
= ( 5 x 6 x 7 x 8 ) x ( 1 x 2 x 3 x 4 + 2 x 3 x 4 x 9 + 3 x 4 x 9 x 10 + 4 x 9 x 10 x 11 + 9 x 10 x 11 x 12 )
= 1680 x ( 24 + 216 + 1080 + 3960 + 11880 )
= 1680 x 17160
= 28,828,800#
2008-03-27 10:37:55 補充:
或者可以這樣:
1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 = 40320
2 x .. x 9 = 362880
3 x .. x 9 = 181440
4 x .. x 11 = 665280
5 x .. x 12 = 19958400