101×99×999+999
=(100+1)×(100-1)×999+999
=(100²-1+1)×999
=10000×999
=9990000
=(100+1)×(100-1)×999+999
=(100²-1)×999+999
=(10000-1+1)×999
=10000×999
=9990000
原式=(100+1)x99x999+999
=【(100+1)x99+1】x999
=(9900+99+1)X999
=10000X999
=9990000
=(100+1)(100-1)*999+999
=999*[(100+1)(100-1)+1]
=999*(10000-1+1)
=9990000
=(100+1)*(100-1)*999+999=[(10000-1)+1]*999=9990000