由 2110 » 2008年9月29日 22:09:09 (p#1492032)
先拆解下面先
123456790x123456788 - 123456789x123456789
123456790 = 123456789 + 1
123456788 = 123456789 - 1
123456790x123456788 - 123456789x123456789 =
(123456789 + 1)(123456789 - 1) - 123456789x123456789
= (123456789^2 - 1 )- 123456789^2
= -1
123456789987654321
-------------------------------------------------------------
123456790x123456788-123456789x123456789
=
123456789987654321
-------------------------------------------------------------
-1
=
-123456789987654321
應該冇錯架啦
.