998*997997-997*998998=
问题描述：
998*997997-997*998998=
答
998*997997=996001006
997*998998=996001006
相减等于0
997*998998=(998-1)*(997997+1001)
=998*997997+998*1001-997997-1001
=998*997997+998998-998998
=998*997997
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