1-2+3-4+5-6+.+2009-2010+2001 简算

问题描述:

1-2+3-4+5-6+.+2009-2010+2001 简算

1-2+3-4+5-6+.+2009-2010+2001
=1+3-2+5-4+7-6……+2001-2010
=1+(3-2)+(5-4)+(7-6)……+(2001-2010)
=1+1+1+1……+1
=1+[(2001-1)÷2]×1
=1+2000÷2
=1+1000
=1001