求1个等差数列,1-3+5-7+9-11+.-1999+2001

问题描述:

求1个等差数列,1-3+5-7+9-11+.-1999+2001

1-3+5-7+9-11+...+1997-1999+2001
=(1-3)+(5-7)+(9-11)+...+(1997-1999)+2001
=(-2)×499+2001
=1003