1+2-3-4+5+6-7-8+.+2001+2002-2003-2044=?

1+2-3-4+5+6-7-8+.+2001+2002-2003-2004
=(1+2-3-4)+(5+6-7-8)+(2001+2002-2003-2004)
=(-4)×501
=-2004
(1/1*3)+(1/3*5)+(1/5*7)+.+(1/99*101)
=(1-1/3)/2+(1/3-1/5)/2+……+(1/99-1/101)/2
=(1-1/101)/2
=50/101