1-1/1*2-1/2*3-1/3*4-1/4*5……-1/2008*2009
=1-(1/1*2+1/2*3+1/3*4+……+1/2009*2010)
=1-(1-1/2+1/2-1/3+1/3-1/4+……+1/2009-1/2010)
=1-(1-1/2010)
=1-2009/2010
=1/2010
1-1/1*2-1/2*3-1/3*4-1/4*5……-1/2008*2009
=1-(1/1*2+1/2*3+1/3*4+……+1/2009*2010)
=1-(1-1/2+1/2-1/3+1/3-1/4+……+1/2009-1/2010)
=1-(1-1/2010)
=1-2009/2010
=1/2010