1x2x3x4x5x6x7x8+2x3x4x5x6x7x8x9+...+5x6x7x8x9x10x11x12=?

1x2x3x4x5x6x7x8+2x3x4x5x6x7x8x9+...+5x6x7x8x9x10x11x12
=1x2x3x4x5x6x7x8+2x3x4x5x6x7x8x9+3x4x5x6x7x8x9x10+4x5x6x7x8x9x10x11+5x6x7x8x9x10x11x12
=40320+362880+1814400+6652800+19958400
=28828800

係咪奧數...=.=|||

1x2x3x4x5x6x7x8+2x3x4x5x6x7x8x9+...+5x6x7x8x9x10x11x12=?

=1x2x3x4x5x6x7x8+2x3x4x5x6x7x8x9+3x4x5x6x7x8x9x10+4x5x6x7x8x9x10x11+5x6x7x8x9x10x11x12

=40320+362880+1814400+6652800+19958400

=403200+1814400+6652800+19958400

=2217600+6652800+19958400

=8870400+19958400

=28828800

我想問下上面個人兄
28,828,800# ← 呢個符號點解
小弟數學差
水平低
未去到高境界
所以唔知你果個符號點解
可唔可以介紹番比我聽
教下小弟呢

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

40320 + 362880 + 1814400 + 6652800 + 19958400
= 28,828,800#

(5x6x7x8)x(1x2x3x4 + 2x3x4x9 + 3x4x9x10+4x9x10x11 +9x10x11x12)
=1680 (24+216+2160+3960+11880)
=1680x18240
=30,643,200