-1-2-3+4-5-6-7+8-9-10-11+12-...-997-998-999+2000=?
问题描述:
-1-2-3+4-5-6-7+8-9-10-11+12-...-997-998-999+2000=?
答
-1-2-3+4-5-6-7+8-9-10-11+12-...-997-998-999+2000
=(-1-2-3+4)+(-5-6-7+8)+……+(-1997-1998-1999+2000)
= -2+(-10)+(-18)+(-26)+……+(-3994)
=【-2+(-3994)】×500÷2
= -3996×250
= -999000