1999+999*999
=1000+999+999*999
=1000+999*(999+1)
=1000*(999+1)
=1000000
999*99*9
=(1000-1)*(100-1)*9
=1000*(100*9-9)-(100*9-9)
=891000-891
=890109
您好!
1999+999*999
=(1000+999)+999*999
=1000+999*(999+1)
=1000+999*1000
=1000+999000
=1000000
你是一个大笨蛋