1989×1999-1988×2000.
问题描述:
1989×1999-1988×2000.
答
1989×1999-1988×2000
=1989×(2000-1)-1988×2000,
=1989×2000-1989×1-1988×2000,
=(1989-1988)×2000-1989,
=1×2000-1989,
=2000-1989,
=11.