999²-1002*998
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999²-1002*998
![999²-1002*998](/uploads/image/z/15402361-49-1.jpg?t=999%26sup2%3B-1002%2A998)
999²-1002*998
=999²-(1000+2)(1000-2)
=999²-1000²+4
=(999+1000)(999-1000)+4
=-1999+4
=-1995
=999²-(1000+2)(1000-2)
=999²-1000²+4
=(999+1000)(999-1000)+4
=-1999+4
=-1995