∵1/2<1
1/3<1/2
1/4<1/3
...
1/2009<1/2008
∴原式=-(1/2-1)-(1/3-1/2)-(1/4-1/3)-(1/5-1/4)...-(1/2009- 1/2008)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+...+1/2008-1/2009
=2008/2009
∵1/2<1
1/3<1/2
1/4<1/3
...
1/2009<1/2008
∴原式=-(1/2-1)-(1/3-1/2)-(1/4-1/3)-(1/5-1/4)...-(1/2009- 1/2008)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+...+1/2008-1/2009
=2008/2009