题目内容
999
×999.
| 998 |
| 999 |
999
×999,
=999+
)×999,
=999×999+
×999,
=×999+998,
=999×1000-999+998,
=999000-(999-998),
=999000-1,
=998999.
| 998 |
| 999 |
=999+
| 998 |
| 999 |
=999×999+
| 998 |
| 999 |
=×999+998,
=999×1000-999+998,
=999000-(999-998),
=999000-1,
=998999.
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