原式=1/2[2/(1x3)+2/(3x5)+······+2/(9x11)]
=1/2(1-1/3+1/3-1/5+······+1/9-1/11)
=1/2(1-1/11)
=1/2 x 10/11
=5/11
注:/为分数线,如:1/2 表示二分之一
原式=1/2[2/(1x3)+2/(3x5)+······+2/(9x11)]
=1/2(1-1/3+1/3-1/5+······+1/9-1/11)
=1/2(1-1/11)
=1/2 x 10/11
=5/11
注:/为分数线,如:1/2 表示二分之一