解:1/2*4+1/4*6+1/6*8+....+1/2006*2008
=1/2*(1/2-1/4)+1/2*(1/4-1/6)+1/2*(1/6-1/8)+....+1/2*(1/2006-1/2008)
=1/2*(1/2-1/4+1/4-1/6+1/6-1/8+...+1/2006-1/2008)
=1/2*(1/2-1/2008)
=1/2*(1004/2008-1/2008)
=1/2*1003/2008
=1003/4016
原式=1/2(1/2-1/4 1/4-1/6......)=1003/2008
做这种题关键是观察
1/(2*4)=1/8=1/2*(1/2-1/4)