1991×19901990-1990×19911991 等于多少?

问题描述:

1991×19901990-1990×19911991 等于多少?

原式=1991*1990*10001-1990*1991*10001=0
放心是没有错的

1991×19901990-1990×19911991
=(1990+1)×19901990-1990×19911991
=1990×19901990+19901990-1990×19911991
=1990×(19901990-19911991)+19901990
=1990×(-10001)+19901990
=-19901990+19901990
=0