观察:1/2=1/(1×2)=1/1-1/2
1/6=1/(2×3)=1/2-1/3
.
1/(2005×2006)=1/2005-1/2006
所以原式=1/1-1/2+1/2+1/3-1/3+1/4-1/4+.+1/2005-1/2006
=1-1/2006
=2005/2006
原式=(1+3+5+...+99)+1/100(1+3+5+...99)=[50*(1+99)/2]*101*100=25*101=2525
观察:1/2=1/(1×2)=1/1-1/2
1/6=1/(2×3)=1/2-1/3
.
1/(2005×2006)=1/2005-1/2006
所以原式=1/1-1/2+1/2+1/3-1/3+1/4-1/4+.+1/2005-1/2006
=1-1/2006
=2005/2006
原式=(1+3+5+...+99)+1/100(1+3+5+...99)=[50*(1+99)/2]*101*100=25*101=2525